[flutter_tools] add missing period to end of filter

[jonahwilliams]

Description

Output on module build:

jonahwilliams-macbookpro2:foo jonahwilliams$ flutter build ios-framework
Running "flutter pub get" in foo...                                 0.4s
Building frameworks for com.example.foo in debug mode...
 ├─Populating Flutter.framework...                                  0.2s
 ├─Adding placeholder App.framework for debug...                   155ms
 ├─Assembling Flutter resources for App.framework...                7.0s
 └─Moving to build/ios/framework/Debug                              0.0s
Building frameworks for com.example.foo in profile mode...
 ├─Populating Flutter.framework...                                  0.2s
 ├─Building Dart AOT for App.framework...                          20.0s
 ├─Assembling Flutter resources for App.framework...                0.1s
 └─Moving to build/ios/framework/Profile                            0.0s
Building frameworks for com.example.foo in release mode...
 ├─Populating Flutter.framework...                                  1.5s
 ├─Building Dart AOT for App.framework...                          16.2s
 ├─Assembling Flutter resources for App.framework...                0.1s
 └─Moving to build/ios/framework/Release                            0.0s
Frameworks written to /Users/jonahwilliams/Documents/foo/build/ios/framework.

[fluttergithubbot]

It looks like this pull request may not have tests. Please make sure to add tests before merging. If you need an exemption to this rule, contact Hixie.

Reviewers: Read the Tree Hygiene page and make sure this patch meets those guidelines before LGTMing.

[jmagman]

LGTM thanks!