Fix broken links from APM-Server 10874

[kilfoyle]

This is an attempt to fix some broken links in the current docs build:

08:57:42 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/apm/agent/python/5.x/api.html contains broken links to:
08:57:42 INFO:build_docs:   - en/apm/guide/8.8/events-api.html#events-api-errors
08:57:42 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/apm/agent/python/6.x/api.html contains broken links to:
08:57:42 INFO:build_docs:   - en/apm/guide/8.8/events-api.html#events-api-errors
08:57:42 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/apm/agent/python/current/api.html contains broken links to:
08:57:42 INFO:build_docs:   - en/apm/guide/8.8/events-api.html#events-api-errors
08:57:42 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/apm/agent/python/master/api.html contains broken links to:
08:57:42 INFO:build_docs:   - en/apm/guide/8.8/events-api.html#events-api-errors

The change would need to be backported from main into 6.x and 5.x.

[kilfoyle]

@elasticmachine run elasticsearch-ci/docs

[kilfoyle]

Closing. The build is fixed using redirects via elastic/apm-server#10891