Bump the default Gradle daemon heap to match what CI already uses (#7152)

A local release build runs R8 over the full app and reliably runs out of
heap at the checked-in 4g default. CI has used 8g for release builds all
along via GRADLE_OPTS, so bring the local default in line with that.

Same reasoning as 6e55f2d7 (#1087), which bumped 2048m to 4g.

gradle.properties

@@ -13,7 +13,10 @@
 # http://www.gradle.org/docs/current/userguide/build_environment.html
 # Specifies the JVM arguments used for the daemon process.
 # The setting is particularly useful for tweaking memory settings.
-org.gradle.jvmargs=-Xmx4g -Dfile.encoding=UTF-8 -XX:+UseG1GC
+# Matches the heap size CI already uses for release builds (see GRADLE_OPTS in
+# .github/workflows/release.yml and nightly.yml) - a local `assembleRelease`/`bundleRelease`
+# runs R8 on the full app and can run out of heap well before 4g on this codebase's size.
+org.gradle.jvmargs=-Xmx8g -Dfile.encoding=UTF-8 -XX:+UseG1GC
 
 # AndroidX package structure to make it clearer which packages are bundled with the
 # Android operating system, and which are packaged with your app"s APK