SOLR-17661: Fix flaky TestLTRQParserPlugin tests

The flaky tests are:
- TestLTRQParserPlugin.ltr_expensiveFeatureRescoring_shouldTimeOutAndReturnPartialResults
- TestLTRQParserPlugin.ltr_expensiveFeatureRescoringAndPartialResultsNotTolerated_shouldRaiseException

These tests have to timeout after the initial search is complete, and
during the reranking phase. The reranking model takes 1 second to load,
so increase the timeout to 800ms so that the search is more likely to
complete in that timeframe.

Author: HoustonPutman

solr/modules/ltr/src/test/org/apache/solr/ltr/TestLTRQParserPlugin.java

@@ -153,7 +153,7 @@ public void ltr_expensiveFeatureRescoring_shouldTimeOutAndReturnPartialResults()
     query.setQuery(solrQuery);
     query.setFields("id", "score");
     query.setRows(4);
-    query.setTimeAllowed(300);
+    query.setTimeAllowed(800);
     query.add("fv", "true");
     query.add("rq", "{!ltr model=slowModel reRankDocs=3}");
 
@@ -187,7 +187,7 @@ public void ltr_expensiveFeatureRescoringAndPartialResultsNotTolerated_shouldRai
     query.setQuery(solrQuery);
     query.setFields("id", "score");
     query.setRows(4);
-    query.setTimeAllowed(300);
+    query.setTimeAllowed(800);
     query.add("partialResults", "false");
     query.add("fv", "true");
     query.add("rq", "{!ltr model=slowModel reRankDocs=3}");