Fix for "regular expression has redundant nested repeat operator" in …

…MySQL slowlog module.

Fix for issue #17086.

The grok pattern used in the MySQL slowlog ingest pipeline uses EXPLAIN pattern with a superfluous * wildcard.

This makes Elasticsearch log a warning seemingly every time the pipeline is used.

filebeat/module/mysql/slowlog/ingest/pipeline.json

@@ -9,7 +9,7 @@
       "pattern_definitions" : {
         "GREEDYMULTILINE": "(.|\n)*",
         "METRICSPACE": "([ #\n]*)",
-        "EXPLAIN": "(# explain:.*\n|#\\s*\n)*"
+        "EXPLAIN": "(# explain:.*\n|#\\s*\n)"
       },
       "ignore_missing": true
     }