chore: remove custom flag to config behavior

Author: diegomarquezp

.kokoro/build.sh

@@ -117,7 +117,7 @@ graalvm)
     ;;
 graalvmA)
     # Run Unit and Integration Tests with Native Image A.
-    NATIVE_IMAGE_OPTIONS="--strict-image-heap" mvn -B ${INTEGRATION_TEST_ARGS} -ntp -Pnative -Penable-integration-tests test "-Dtest=com.google.cloud.spanner.jdbc.it.**"
+    mvn -B ${INTEGRATION_TEST_ARGS} -ntp -Pnative -Penable-integration-tests test "-Dtest=com.google.cloud.spanner.jdbc.it.**"
     RETURN_CODE=$?
     ;;
 samples)