Raise gradle wrapper version of legacy project (flutter#6132)

When running `flutter create` for a new plugin on `master`, this error is printed from the legacy build_all_packages test.

![Screenshot 2024-02-09 at 3 08 35�PM](https://github.com/flutter/packages/assets/10687576/0f22382c-6c88-4aab-8e80-d385ef2892fa)

It looks like only 6.7.1 is required to work with new plugins, so this is only a minor bump.

Author: bparrishMines

.ci/legacy_project/README.md

@@ -39,3 +39,6 @@ and then deleting everything but `android/` from it:
   jcenter.bintray.com shutdown.
 - Update `compileSdkVersion` from 30 to 33 to maintain compatibility
   with plugins that use API 34.
+- Updates `gradle-wrapper.properties` from `6.7` to `6.7.1`, to add
+  support for the Kotlin gradle plugin. If a user runs into this
+  error, the error message is clear on how to upgrade.

.ci/legacy_project/all_packages/android/gradle/wrapper/gradle-wrapper.properties

@@ -3,4 +3,4 @@ distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
 zipStoreBase=GRADLE_USER_HOME
 zipStorePath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-6.7-all.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-6.7.1-all.zip