Fix lint warning failing the tree

[reidbaker]

dart analyze fails at tip of tree. Not sure why the tree isnt red but it should be .

warning • packages/flutter_tools/test/commands.shard/permeable/create_test.dart:3663:68 • The '!' will have no effect because the receiver
          can't be null. Try removing the '!' operator. • unnecessary_non_null_assertion
warning • packages/flutter_tools/test/commands.shard/permeable/create_test.dart:4340:26 • The '!' will have no effect because the receiver
          can't be null. Try removing the '!' operator. • unnecessary_non_null_assertion

Pre-launch Checklist

• I read the [Contributor Guide] and followed the process outlined there for submitting PRs.
• I read the [Tree Hygiene] wiki page, which explains my responsibilities.
• I read and followed the [Flutter Style Guide], including [Features we expect every widget to implement].
• I signed the [CLA].
• I listed at least one issue that this PR fixes in the description above.
• I updated/added relevant documentation (doc comments with ///).
• I added new tests to check the change I am making, or this PR is [test-exempt].
• I followed the [breaking change policy] and added [Data Driven Fixes] where supported.
• All existing and new tests are passing.

[goderbauer]

That ! should be required here, though. Pubspec.environment [1] is a nullable type that is assigned to a non-nullable variable.

[1] https://pub.dev/documentation/pubspec_parse/1.3.0/pubspec_parse/Pubspec/environment.html

[goderbauer]

Can you run package updated-packages to see if that fixes the problem for you?

[reidbaker]

I ran flutter update-package and without any file changes the lint error went away.