i18n: Fix makemessages not walking subdirectories.
i18n: Fix makemessages not walking subdirectories.

Fixes an issue noticed in #14881.

punchagan/zulip,showell/zulip,timabbott/zulip,shubhamdhama/zulip,synicalsyntax/zulip,andersk/zulip,timabbott/zulip,hackerkid/zulip,andersk/zulip,kou/zulip,zulip/zulip,punchagan/zulip,synicalsyntax/zulip,timabbott/zulip,timabbott/zulip,andersk/zulip,rht/zulip,rht/zulip,eeshangarg/zulip,timabbott/zulip,andersk/zulip,andersk/zulip,punchagan/zulip,showell/zulip,kou/zulip,punchagan/zulip,hackerkid/zulip,showell/zulip,brainwane/zulip,shubhamdhama/zulip,rht/zulip,timabbott/zulip,kou/zulip,synicalsyntax/zulip,rht/zulip,shubhamdhama/zulip,zulip/zulip,hackerkid/zulip,kou/zulip,punchagan/zulip,showell/zulip,synicalsyntax/zulip,andersk/zulip,kou/zulip,zulip/zulip,rht/zulip,synicalsyntax/zulip,zulip/zulip,kou/zulip,shubhamdhama/zulip,brainwane/zulip,synicalsyntax/zulip,eeshangarg/zulip,brainwane/zulip,punchagan/zulip,synicalsyntax/zulip,eeshangarg/zulip,brainwane/zulip,eeshangarg/zulip,eeshangarg/zulip,eeshangarg/zulip,brainwane/zulip,rht/zulip,zulip/zulip,hackerkid/zulip,punchagan/zulip,eeshangarg/zulip,shubhamdhama/zulip,rht/zulip,kou/zulip,shubhamdhama/zulip,showell/zulip,andersk/zulip,timabbott/zulip,hackerkid/zulip,brainwane/zulip,zulip/zulip,showell/zulip,hackerkid/zulip,showell/zulip,zulip/zulip,hackerkid/zulip,shubhamdhama/zulip,brainwane/zulip