Remove incorrect Coveralls badge. (#26550)
Remove incorrect Coveralls badge. (#26550)

The code coverage for the repository seems to be ~85% while the coverage reported by the Coveralls badge is 100%.
cbracken/flutter,Hixie/flutter,Hixie/flutter,flutter/flutter,tvolkert/flutter,cbracken/flutter,tvolkert/flutter,tvolkert/flutter,flutter/flutter,flutter/flutter,cbracken/flutter,flutter/flutter,cbracken/flutter,flutter/flutter,flutter/flutter,Hixie/flutter,cbracken/flutter,flutter/flutter,flutter/flutter,Hixie/flutter,tvolkert/flutter,flutter/flutter,tvolkert/flutter,tvolkert/flutter,tvolkert/flutter,tvolkert/flutter,Hixie/flutter,cbracken/flutter,Hixie/flutter,tvolkert/flutter,cbracken/flutter,cbracken/flutter,cbracken/flutter,Hixie/flutter,Hixie/flutter,cbracken/flutter,Hixie/flutter,tvolkert/flutter,flutter/flutter,Hixie/flutter