Fix yaml as @ is forbidden in YAML 1.2
Fix yaml as @ is forbidden in YAML 1.2

http://www.yaml.org/spec/1.2/spec.html#id2772075

(PR done on `2.5` branch, but this issue persists also in `2.6`, `2.7` and `master`)

GulDmitry/music-diff,twisted-socket/stage-plots,formapro-forks/api-basic,fabpot/symfony-standard,black-project/black-standard,GulDmitry/music-diff,taylankasap/symfony-standard,wachterjohannes/sulu-standard,glavweb/symfony-standard,uttam-vi/pardawala,SymfonyId/Skeleton,UxorialRook/symfony-standard,ovelasquez/ussi,fahadonline/sulu,Spea/symfony-standard,vincentchalamon/phpunit-bridge,wachterjohannes/sulu-standard,GulDmitry/music-diff,ctrl-f5/symfony-standard,propelorm/symfony-propel-edition,shadowtje1990/symfony_todo_api,irro/MastoAlliance,egeloen/symfony-standard,unewochialat/symfony-standard,gencer/symfony-standard,ucay/Skeleton,xabbuh/symfony-standard,orodsem/trout,HasClass0/standard-edition,the-software-factory/superhero-api,orodsem/trout,jakzal/symfony-standard,phospr/symfony-starter,vincentaubert/symfony-standard,symfony/symfony-standard,apnet/symfony-standard-edition,papaavola/symfony-standard,yhoiseth/notelite.net,mweimerskirch/symfony-standard,platformsh/platformsh-example-symfony,ucay/Skeleton,fahadonline/sulu,dkarvounaris/symfony-standard,NoUseFreak/StandardEdition,symfony-cmf/standard-edition,rajkamalganeshvivid/symfony-standard,Cartesia/01,Soullivaneuh/symfony-standard,stof/symfony-standard,jbdelhommeau/symfony-standard,symfony-cmf/standard-edition,sulu-io/sulu-standard,irro/MastoAlliance,tristanbes/symfony-standard,fduch/symfony-standard-workflow,trsteel88/symfony-standard,aerrasti/iemedebe,ovelasquez/ussi,bamarni/symfony-docker,yhoiseth/notelite.net,debruyne0/symfony,pjcdawkins/tmp-symfony-demo,theodo/theodo-kata,formapro-forks/api-basic,sulu-io/sulu-standard,ovelasquez/ussi,dkarvounaris/symfony-standard,glavweb/symfony-standard,apnet/symfony-standard-edition,jbdelhommeau/symfony-standard,simonjcarr/symfony_rest,the-software-factory/superhero-api,bocharsky-bw/symfony-standard,NoUseFreak/StandardEdition,spolischook/standard-edition,fabpot/symfony-standard,ewgRa/symfony-standard,Spea/symfony-standard,black-project/black-standard,havvg/symfony-propel-edition,javiereguiluz/symfony-standard,yelmontaser/symfony-standard,vincentchalamon/phpunit-bridge,fahadonline/sulu,NoUseFreak/StandardEdition,fahadonline/sulu,lyrixx/symfony-standard,shadowtje1990/symfony_todo_api,rajkamalganeshvivid/symfony-standard,theodo/theodo-kata,xiaobudongzhang/symfony-standard,havvg/symfony-standard-propel,skafandri/blog,zanderbaldwin/symfony-layers,kmelia/fresh-symfony,AlexeyKupershtokh/symfony-standard,dunglas/symfony-standard,dunglas/symfony-standard,zanderbaldwin/symfony-layers,trsteel88/symfony-standard,Cartesia/01,stof/symfony-standard,OskarStark/symfony-standard,jakzal/symfony-standard,UxorialRook/symfony-standard,b00giZm/symfony-boilerplate-app,RuntyCybin/symfony-standard,bamarni/symfony-docker,havvg/symfony-propel-edition,Soullivaneuh/symfony-standard,OskarStark/symfony-standard,HasClass0/standard-edition,Baachi/symfony-standard,spolischook/standard-edition,vincentaubert/symfony-standard,WolfMicrosystems/symfony-wms,apnet/symfony-standard-edition,tristanbes/symfony-standard,shamcode/symfony-testing,kmelia/fresh-symfony,proteichik/testApp,xiaobudongzhang/symfony-standard,papaavola/symfony-standard,b00giZm/symfony-boilerplate-app,Cartesia/01,sulu-io/sulu-standard,Clastic/StandardEdition,Rvanlaak/symfony-standard,yelmontaser/symfony-standard,orodsem/trout,ctrl-f5/symfony-standard,pjcdawkins/tmp-symfony-demo,unewochialat/symfony-standard,kmelia/fresh-symfony,SymfonyId/Skeleton,proteichik/testApp,wachterjohannes/sulu-standard,ewgRa/symfony-standard,WolfMicrosystems/symfony-wms,Baachi/symfony-standard,propelorm/symfony-propel-edition,ucay/Skeleton,shamcode/symfony-testing,Tobion/symfony-standard,taylankasap/symfony-standard,bocharsky-bw/symfony-standard,liip-forks/symfony-standard,aerrasti/iemedebe,debruyne0/symfony,uttam-vi/pardawala,b00giZm/symfony-boilerplate-app,GulDmitry/music-diff,gencer/symfony-standard,phospr/symfony-starter,Clastic/StandardEdition,egeloen/symfony-standard,symfony/symfony-standard,liip-forks/symfony-standard,twisted-socket/stage-plots,RuntyCybin/symfony-standard,simonjcarr/symfony_rest,fduch/symfony-standard-workflow,Tobion/symfony-standard,Clastic/StandardEdition,uttam-vi/pardawala,lyrixx/symfony-standard,platformsh/platformsh-example-symfony,javiereguiluz/symfony-standard,umpirsky/symfony-standard,havvg/symfony-standard-propel,AlexeyKupershtokh/symfony-standard,skafandri/blog,mweimerskirch/symfony-standard,umpirsky/symfony-standard