Update few links in docs (flutter#172166)

Co-authored-by: Matan Lurey <[email protected]>

Author: mdebbar

docs/infra/Updating-dependencies-in-Flutter.md

@@ -1,4 +1,4 @@
-Instead of manually updating dependencies in a `pubspec.yaml` file, use the [`update-packages`](packages/flutter_tools/lib/src/commands/update_packages.dart) CLI tool:
+Instead of manually updating dependencies in a `pubspec.yaml` file, use the [`update-packages`](/packages/flutter_tools/lib/src/commands/update_packages.dart) CLI tool:
 
 ## To update all dependencies:
 
@@ -8,7 +8,7 @@ Instead of manually updating dependencies in a `pubspec.yaml` file, use the [`up
 
 Sometimes you need to prevent a dependency from being updated when you run `flutter update-packages --force-upgrade`.
 
-In that case, first pin the dependency in [`kManuallyPinnedDependencies`](https://github.com/flutter/flutter/blob/5bd34ef541575eddae6aaa82fc76a59ae7e464c3/packages/flutter_tools/lib/src/update_packages_pins.dart#L17) and include a comment with a link to an issue to unpin the dependency.
+In that case, first pin the dependency in [`kManuallyPinnedDependencies`](/packages/flutter_tools/lib/src/update_packages_pins.dart) and include a comment with a link to an issue to unpin the dependency.
 
 You can then re-run `flutter update-packages --force-upgrade`.