Increase heap size in Java linkage monitor test

This is a partial cherry-pick of
da85a3a96fb18e5e06536b9c15af7e31d9f22c76 and should fix Java linkage
monitor CI failures on the 22.x branch.
diff --git a/.github/workflows/test_java.yml b/.github/workflows/test_java.yml
index cea3223..0ef1eec 100644
--- a/.github/workflows/test_java.yml
+++ b/.github/workflows/test_java.yml
@@ -70,4 +70,4 @@
       - name: Download Linkage Monitor
         run: curl -v -O "https://storage.googleapis.com/cloud-opensource-java-linkage-monitor/linkage-monitor-latest-all-deps.jar"
       - name: Fails if there's new linkage errors compared with baseline
-        run: java -Xmx2048m -jar linkage-monitor-latest-all-deps.jar com.google.cloud:libraries-bom
+        run: java -Xmx4096m -jar linkage-monitor-latest-all-deps.jar com.google.cloud:libraries-bom