Remove gradle_deprecated_settings test app, and remove reference from lockfile exclusion yaml (flutter#161622)

The test was intentionally broken by
flutter#160947. That PR removed the CI
configuration to run the test, but the autoroller (which was previously
turned off) runs a gradle command in all android subdirectories, so the
fact that the directory wasn't deleted is blocking turning the
autoroller back on:


https://logs.chromium.org/logs/flutter/buildbucket/cr-buildbucket/8725731612391969937/+/u/run_roll-packages_script/stdout

```
[stderr] * What went wrong:
[stderr] A problem occurred evaluating script.
[stderr] > You are applying Flutter's main Gradle plugin imperatively using the apply script method, which is not possible anymore. Migrate to applying Gradle plugins with the declarative plugins block: https://flutter.dev/to/flutter-gradle-plugin-apply
```

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we expect every widget to implement].
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- [ ] I listed at least one issue that this PR fixes in the description
above.
- [x] I updated/added relevant documentation (doc comments with `///`).
- [x] I added new tests to check the change I am making, or this PR is
[test-exempt].
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Fixes] where supported.
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Co-authored-by: Gray Mackall <mackall@google.com>

Author: 2 people