Fix redundant operator in activemq ingest pipeline (elastic#17428)

Grok processor has a redundant `*` operator in a regular expression,
which causes the following warning to be printed to the Elasticsearch
logs every time the pipeline is loaded:

```
regular expression has redundant nested repeat operator * /(?<TIMESTAMP_ISO8601:timestamp>(?:(?>\d\d){1,2})-(?:(?:0?[1-9]|1[0-2]))-(?:(?:(?:0[1-9])|(?:[12][0-9])|(?:3[01])|[1-9]))[T ](?:(?:2[0123]|[01][0-9])):?(?:(?:[0-5][0-9]))(?::?(?:(?:(?:[0-5]?[0-9]|60)(?:[:.,][0-9]+)?)))?(?:(?:Z|[+-](?:(?:2[0123]|[01]?[0-9]))(?::?(?:(?:[0-5][0-9])))))?)(?:\s*)\|(?:\s*)(?<LOGLEVEL:log.level>([Aa]lert|ALERT|[Tt]race|TRACE|[Dd]ebug|DEBUG|[Nn]otice|NOTICE|[Ii]nfo|INFO|[Ww]arn?(?:ing)?|WARN?(?:ING)?|[Ee]rr?(?:or)?|ERR?(?:OR)?|[Cc]rit?(?:ical)?|CRIT?(?:ICAL)?|[Ff]atal|FATAL|[Ss]evere|SEVERE|EMERG(?:ENCY)?|[Ee]merg(?:ency)?))(?:\s*)\|(?:\s*)(?<NOPIPEGREEDYDATA:message>((?! \|).)*)(?:\s*)\|(?:\s*)(?<NOPIPEGREEDYDATA:activemq.caller>((?! \|).)*)(?:\s*)\|(?:\s*)(?<THREAD_NAME:activemq.thread>((?!
).)*)(?:\s*)?(?<GREEDYMULTILINE:activemq.log.stack_trace>(.|\n|\t)*)/
```

CHANGELOG.next.asciidoc

@@ -105,6 +105,7 @@ https://github.com/elastic/beats/compare/v7.0.0-alpha2...master[Check the HEAD d
 - Fixed a mapping exception when ingesting Logstash plain logs (7.4+) with pipeline ids containing non alphanumeric chars. {issue}17242[17242] {pull}17243[17243]
 - Fixed MySQL slowlog module causing "regular expression has redundant nested repeat operator" warning in Elasticsearch. {issue}17086[17086] {pull}17156[17156]
 - Fix `elasticsearch.audit` data ingest pipeline to be more forgiving with date formats found in Elasticsearch audit logs. {pull}17406[17406]
+- Fixed activemq module causing "regular expression has redundant nested repeat operator" warning in Elasticsearch. {pull}17428[17428]
 
 *Heartbeat*
 

x-pack/filebeat/module/activemq/log/ingest/pipeline.yml

@@ -8,7 +8,7 @@ processors:
         NOPIPEGREEDYDATA: "((?! \\|).)*"
         THREAD_NAME: "((?! \n).)*"
       patterns:
-        - "%{TIMESTAMP_ISO8601:timestamp}%{SPACE}\\|%{SPACE}%{LOGLEVEL:log.level}%{SPACE}\\|%{SPACE}%{NOPIPEGREEDYDATA:message}%{SPACE}\\|%{SPACE}%{NOPIPEGREEDYDATA:activemq.caller}%{SPACE}\\|%{SPACE}%{THREAD_NAME:activemq.thread}%{SPACE}?%{GREEDYMULTILINE:activemq.log.stack_trace}"
+        - "%{TIMESTAMP_ISO8601:timestamp}%{SPACE}\\|%{SPACE}%{LOGLEVEL:log.level}%{SPACE}\\|%{SPACE}%{NOPIPEGREEDYDATA:message}%{SPACE}\\|%{SPACE}%{NOPIPEGREEDYDATA:activemq.caller}%{SPACE}\\|%{SPACE}%{THREAD_NAME:activemq.thread}%{SPACE}%{GREEDYMULTILINE:activemq.log.stack_trace}"
       ignore_missing: true
   - date:
       if: "ctx.event.timezone == null"