build: Upgrade Gradle to 9.6.1 (#5863)

Keeps the build on the latest Gradle patch release.

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

Author: runningcode

gradle/wrapper/gradle-wrapper.properties

@@ -1,6 +1,6 @@
 distributionBase=GRADLE_USER_HOME
 distributionPath=wrapper/dists
-distributionUrl=https\://services.gradle.org/distributions/gradle-9.5.1-bin.zip
+distributionUrl=https\://services.gradle.org/distributions/gradle-9.6.1-bin.zip
 networkTimeout=10000
 retries=0
 retryBackOffMs=500