[TEST] Fix failure due to exception message in java11 (elastic#32321)

Java 11 uses more verbose exceptions messages, causing this assertion
to fail.  Changed the test to be less restrictive and only look
for the classes we care about.

Author: polyfractal

x-pack/plugin/rollup/src/test/java/org/elasticsearch/xpack/rollup/RollupResponseTranslationTests.java

@@ -509,10 +509,12 @@ public void testMismatch() throws IOException {
         BigArrays bigArrays = new MockBigArrays(new MockPageCacheRecycler(Settings.EMPTY), new NoneCircuitBreakerService());
         ScriptService scriptService = mock(ScriptService.class);
         InternalAggregation.ReduceContext reduceContext = new InternalAggregation.ReduceContext(bigArrays, scriptService, true);
-        Exception e = expectThrows(RuntimeException.class,
+        ClassCastException e = expectThrows(ClassCastException.class,
                 () -> RollupResponseTranslator.combineResponses(msearch, reduceContext));
-        assertThat(e.getMessage(), equalTo("org.elasticsearch.search.aggregations.metrics.geobounds.InternalGeoBounds " +
-                "cannot be cast to org.elasticsearch.search.aggregations.InternalMultiBucketAggregation"));
+        assertThat(e.getMessage(),
+            containsString("org.elasticsearch.search.aggregations.metrics.geobounds.InternalGeoBounds"));
+        assertThat(e.getMessage(),
+            containsString("org.elasticsearch.search.aggregations.InternalMultiBucketAggregation"));
     }
 
     public void testDateHisto() throws IOException {