[Documentation] When updating kgp minimum document additional changes that are required (#171819)

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Author: reidbaker

packages/flutter_tools/gradle/src/main/kotlin/DependencyVersionChecker.kt

@@ -88,6 +88,8 @@ object DependencyVersionChecker {
     // Before updating any "error" version, ensure that you have updated the corresponding
     // "warn" version for a full release to provide advanced warning. See
     // flutter.dev/go/android-dependency-versions for more.
+    // Advice for maintainers for other areas of code that are impacted are documented
+    // in packages/flutter_tools/lib/src/android/README.md.
     @VisibleForTesting internal val warnGradleVersion: Version = Version(8, 7, 2)
 
     @VisibleForTesting internal val errorGradleVersion: Version = Version(8, 3, 0)

packages/flutter_tools/lib/src/android/README.md

@@ -50,6 +50,10 @@ When updating the Kotlin Gradle Plugin (KGP) version used in project templates
 (`templateKotlinGradlePluginVersion`), make sure that the framework integration
 & benchmark tests are running with at least this KGP version.
 
+When updating the `warnKGPVersion` or `errorKGPVersion` ensure that versions used in
+`dev/tools/bin/generate_gradle_lockfiles.dart` are updated if needed then regenerate
+build.gradle(.kts) files.
+
 For information about the latest version, check https://kotlinlang.org/docs/releases.html#release-details.
 
 #### The Android Gradle Plugin (AGP)