Limit the languages used for notification mailer test (#6487)
Limit the languages used for notification mailer test (#6487)

Some available languages lack translations for notification mails. Now it
tests for two languages which is certain to have required translations:
German and English.

German is the language the current project owner, Eugen Rochko speaks, and
providing English translations for new messages is de facto mandatory.
dunn/mastodon,cybrespace/mastodon,Chronister/mastodon,SerCom-KC/mastodon,d6rkaiz/mastodon,increments/mastodon,mosaxiv/mastodon,musashino205/mastodon,cobodo/mastodon,anon5r/mastonon,WitchesTown/mastodon,pinfort/mastodon,cybrespace/mastodon,anon5r/mastonon,ykzts/mastodon,TheInventrix/mastodon,SerCom-KC/mastodon,danhunsaker/mastodon,h3zjp/mastodon,pointlessone/mastodon,mimumemo/mastodon,MastodonCloud/mastodon,WitchesTown/mastodon,anon5r/mastonon,dwango/mastodon,MastodonCloud/mastodon,unarist/mastodon,pixiv/mastodon,tootsuite/mastodon,increments/mastodon,blackle/mastodon,ambition-vietnam/mastodon,danhunsaker/mastodon,salvadorpla/mastodon,unarist/mastodon,TheInventrix/mastodon,ikuradon/mastodon,amazedkoumei/mastodon,mosaxiv/mastodon,masto-donte-com-br/mastodon,lynlynlynx/mastodon,glitch-soc/mastodon,riku6460/chikuwagoddon,kazh98/social.arnip.org,dwango/mastodon,rutan/mastodon,rutan/mastodon,vahnj/mastodon,Arukas/mastodon,tootsuite/mastodon,amazedkoumei/mastodon,tri-star/mastodon,Ryanaka/mastodon,tateisu/mastodon,Chronister/mastodon,ikuradon/mastodon,yukimochi/mastodon,gol-cha/mastodon,TheInventrix/mastodon,mstdn-jp/mastodon,d6rkaiz/mastodon,mosaxiv/mastodon,cobodo/mastodon,cybrespace/mastodon,tri-star/mastodon,mstdn-jp/mastodon,honpya/taketodon,kazh98/social.arnip.org,theoria24/mastodon,NS-Kazuki/mastodon,rainyday/mastodon,Arukas/mastodon,d6rkaiz/mastodon,im-in-space/mastodon,lindwurm/mastodon,Ryanaka/mastodon,dunn/mastodon,primenumber/mastodon,kirakiratter/mastodon,musashino205/mastodon,d6rkaiz/mastodon,koba-lab/mastodon,lindwurm/mastodon,TheInventrix/mastodon,Kirishima21/mastodon,theoria24/mastodon,tateisu/mastodon,res-ac/mstdn.res.ac,masarakki/mastodon,anon5r/mastonon,rekif/mastodon,imas/mastodon,vahnj/mastodon,primenumber/mastodon,riku6460/chikuwagoddon,gol-cha/mastodon,kirakiratter/mastodon,MitarashiDango/mastodon,MastodonCloud/mastodon,salvadorpla/mastodon,mstdn-jp/mastodon,blackle/mastodon,imas/mastodon,tri-star/mastodon,imas/mastodon,tateisu/mastodon,ikuradon/mastodon,tootsuite/mastodon,salvadorpla/mastodon,summoners-riftodon/mastodon,dwango/mastodon,yi0713/mastodon,pointlessone/mastodon,yukimochi/mastodon,masarakki/mastodon,clworld/mastodon,gol-cha/mastodon,WitchesTown/mastodon,masarakki/mastodon,res-ac/mstdn.res.ac,mimumemo/mastodon,Chronister/mastodon,blackle/mastodon,increments/mastodon,NS-Kazuki/mastodon,hugogameiro/mastodon,ykzts/mastodon,lynlynlynx/mastodon,Kirishima21/mastodon,unarist/mastodon,im-in-space/mastodon,kazh98/social.arnip.org,maa123/mastodon,danhunsaker/mastodon,Nyoho/mastodon,maa123/mastodon,kirakiratter/mastodon,rutan/mastodon,kirakiratter/mastodon,KnzkDev/mastodon,5thfloor/ichiji-social,mhffdq/mastodon,tootsuite/mastodon,summoners-riftodon/mastodon,yi0713/mastodon,tootcafe/mastodon,rutan/mastodon,lynlynlynx/mastodon,tootcafe/mastodon,honpya/taketodon,KnzkDev/mastodon,tri-star/mastodon,Ryanaka/mastodon,maa123/mastodon,PlantsNetwork/mastodon,cobodo/mastodon,h3zjp/mastodon,mhffdq/mastodon,sylph-sin-tyaku/mastodon,masto-donte-com-br/mastodon,unarist/mastodon,mhffdq/mastodon,MastodonCloud/mastodon,koba-lab/mastodon,hugogameiro/mastodon,rekif/mastodon,pso2club/mastodon,pixiv/mastodon,Chronister/mastodon,mhffdq/mastodon,mstdn-jp/mastodon,clworld/mastodon,koba-lab/mastodon,musashino205/mastodon,summoners-riftodon/mastodon,vahnj/mastodon,tootcafe/mastodon,blackle/mastodon,koba-lab/mastodon,Nyoho/mastodon,yukimochi/mastodon,cybrespace/mastodon,glitch-soc/mastodon,amazedkoumei/mastodon,imas/mastodon,masto-donte-com-br/mastodon,sylph-sin-tyaku/mastodon,Kirishima21/mastodon,KnzkDev/mastodon,hugogameiro/mastodon,yi0713/mastodon,amazedkoumei/mastodon,5thfloor/ichiji-social,pso2club/mastodon,musashino205/mastodon,pinfort/mastodon,honpya/taketodon,ambition-vietnam/mastodon,ykzts/mastodon,res-ac/mstdn.res.ac,pixiv/mastodon,NS-Kazuki/mastodon,Nyoho/mastodon,Ryanaka/mastodon,SerCom-KC/mastodon,abcang/mastodon,WitchesTown/mastodon,lindwurm/mastodon,mosaxiv/mastodon,honpya/taketodon,lindwurm/mastodon,primenumber/mastodon,yi0713/mastodon,theoria24/mastodon,tateisu/mastodon,ikuradon/mastodon,ambition-vietnam/mastodon,danhunsaker/mastodon,pinfort/mastodon,h3zjp/mastodon,glitch-soc/mastodon,riku6460/chikuwagoddon,NS-Kazuki/mastodon,rainyday/mastodon,kazh98/social.arnip.org,MitarashiDango/mastodon,mimumemo/mastodon,maa123/mastodon,abcang/mastodon,hugogameiro/mastodon,riku6460/chikuwagoddon,pso2club/mastodon,KnzkDev/mastodon,cobodo/mastodon,SerCom-KC/mastodon,rainyday/mastodon,salvadorpla/mastodon,ykzts/mastodon,glitch-soc/mastodon,PlantsNetwork/mastodon,dunn/mastodon,yukimochi/mastodon,5thfloor/ichiji-social,dwango/mastodon,pso2club/mastodon,PlantsNetwork/mastodon,h3zjp/mastodon,masarakki/mastodon,pinfort/mastodon,theoria24/mastodon,masto-donte-com-br/mastodon,5thfloor/ichiji-social,TheInventrix/mastodon,dunn/mastodon,clworld/mastodon,mimumemo/mastodon,pixiv/mastodon,rekif/mastodon,sylph-sin-tyaku/mastodon,im-in-space/mastodon,abcang/mastodon,rekif/mastodon,Arukas/mastodon,vahnj/mastodon,Nyoho/mastodon,Kirishima21/mastodon,rainyday/mastodon,primenumber/mastodon,clworld/mastodon,res-ac/mstdn.res.ac,Arukas/mastodon,PlantsNetwork/mastodon,increments/mastodon,MitarashiDango/mastodon,abcang/mastodon,sylph-sin-tyaku/mastodon,ambition-vietnam/mastodon,vahnj/mastodon,im-in-space/mastodon,tootcafe/mastodon,summoners-riftodon/mastodon,MitarashiDango/mastodon,pointlessone/mastodon,gol-cha/mastodon,lynlynlynx/mastodon,pointlessone/mastodon