Mark nonflaky tests as such (#65054)
Mark nonflaky tests as such (#65054)

Those 2 tests have been green for the last 10 runs
tvolkert/flutter,cbracken/flutter,cbracken/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,flutter/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,flutter/flutter,flutter/flutter,flutter/flutter,cbracken/flutter,flutter/flutter,flutter/flutter,tvolkert/flutter,flutter/flutter,cbracken/flutter,cbracken/flutter,Hixie/flutter,cbracken/flutter,tvolkert/flutter,cbracken/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,Hixie/flutter,flutter/flutter,Hixie/flutter,tvolkert/flutter,Hixie/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,cbracken/flutter,Hixie/flutter