Remove target platform override on the gallery. (#51920)
Remove target platform override on the gallery. (#51920)

Remove a target platform override that is no longer needed (I missed this in #51519).
flutter/flutter,tvolkert/flutter,cbracken/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,flutter/flutter,cbracken/flutter,tvolkert/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,cbracken/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,flutter/flutter,flutter/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter