Revert "Add false_allow_templates as a dynamic mapping option (#18825)"

[andrross]

This reverts commit 9f28ef8.

Lots of test failures blocking PRs for the newly added yaml test.

Example build failure: https://build.ci.opensearch.org/job/gradle-check/62321/#showFailuresLink

Check List

• Functionality includes testing.

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
For more information on following Developer Certificate of Origin and signing off your commits, please check here.

[andrross]

FYI @bruce-hong-glean @gaobinlong

[github-actions]

❌ Gradle check result for 5839a56: FAILURE

Please examine the workflow log, locate, and copy-paste the failure(s) below, then iterate to green. Is the failure a flaky test unrelated to your change?

[bruce-hong-glean]

Sorry about that, I didn't realize updating the version to 3.3.0 in the test file caused my local testing to skip that test when it was executing. I'll put up a new PR with the working test.

[github-actions]

✅ Gradle check result for 5839a56: SUCCESS

[codecov]

Codecov Report

❌ Patch coverage is 92.30769% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 72.86%. Comparing base (8f310f5) to head (5839a56).
⚠️ Report is 3 commits behind head on main.

Files with missing lines	Patch %	Lines
...va/org/opensearch/index/mapper/DocumentParser.java	91.66%	1 Missing ⚠️

Additional details and impacted files

@@             Coverage Diff              @@
##               main   #19061      +/-   ##
============================================
- Coverage     72.89%   72.86%   -0.04%     
+ Complexity    69405    69401       -4     
============================================
  Files          5647     5647              
  Lines        319084   319084              
  Branches      46157    46157              
============================================
- Hits         232594   232491     -103     
- Misses        67700    67809     +109     
+ Partials      18790    18784       -6     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.

[bruce-hong-glean]

I have a PR removing the offending tests (they're testing invalid types and shouldn't exist to begin with) as a draft here.

lmk if you'd prefer to merge in this revert, and then have the draft PR (+ these reverted changes) merged in separately, if just fix-forward with the draft PR.

[andrross]

@bruce-hong-glean Apologies, I clicked merge on the revert before seeing your comments about having the fix. Please integrate your fix back into the original change and we'll get it merged again. Thanks!