[activemq] Update integration package to remove unnecessary fields

[kush-elastic]

• Bug

What does this PR do?

This PR contains a minor cleanup for ActiveMQ integration. It removes the 2 fields which were present in fields.yml . These two fields are activemq.log.log_stack_trace and activemq.log.message which are regrouped in error.stack_trace and message fields. Since these fields are replaced they are no longer required in fields.yml.
As we know that release tag got deprecated but recently got added by ellis-elastic in this PR , so removed that tag as a part of this bugfix PR
The changes which are made do not affect the existing functionality of the integration at all and are just a cleanup to the integration.

Checklist

• I have reviewed tips for building integrations and this pull request is aligned with them.
• I have verified that all data streams collect metrics or logs.
• I have added an entry to my package's changelog.yml file.
• I have verified that Kibana version constraints are current according to guidelines.

How to test this PR locally

• Clone integrations repo.
• Install elastic-package locally.
• Start elastic stack using elastic-package.
• Move to integrations/packages/activemq directory.
• Run the following command to run tests.

elastic-package test

[elasticmachine]

💚 Build Succeeded

the below badges are clickable and redirect to their specific view in the CI or DOCS

Expand to view the summary

Build stats

• Start Time: 2022-07-28T10:26:19.340+0000

• Duration: 19 min 21 sec

Test stats 🧪

Test	Results
Failed	0
Passed	26
Skipped	0
Total	26

🤖 GitHub comments

To re-run your PR in the CI, just comment with:

• /test : Re-trigger the build.

[elasticmachine]

🌐 Coverage report

Name	Metrics % (covered/total)	Diff
Packages	100.0% (2/2)	💚
Files	100.0% (2/2)	💚 2.953
Classes	100.0% (2/2)	💚 2.953
Methods	95.833% (23/24)	👍 6.193
Lines	83.838% (83/99)	👎 -7.606
Conditionals	100.0% (0/0)	💚

[yug-rajani]

LGTM!