License update - Batch 28

[mossmana]

Updates the license headers for:

1. packages/devtools_app/lib/src/shared/charts/README.md
2. packages/devtools_app/lib/src/shared/charts/chart.dart
3. packages/devtools_app/lib/src/shared/charts/chart_controller.dart
4. packages/devtools_app/lib/src/shared/charts/chart_trace.dart
5. packages/devtools_app/lib/src/shared/charts/flame_chart.dart
6. packages/devtools_app/lib/src/shared/charts/treemap.dart
7. packages/devtools_app/test/shared/charts/flame_chart_test.dart
8. packages/devtools_app/test/shared/charts/treemap_test.dart

#8216

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 the [Flutter Style Guide] recently, and have followed its advice.
• 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 there is a reason for not adding tests.