Update connecting.asciidoc

[lcawl]

Relates to elastic/docs#2518

In particular, this PR is related to the following link issues:

10:11:43 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/enterprise-search-clients/php/8.0/connecting.html contains broken links to:
10:11:43 INFO:build_docs:   - en/kibana/master/api-keys.html
10:11:43 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/enterprise-search-clients/php/8.1/connecting.html contains broken links to:
10:11:43 INFO:build_docs:   - en/kibana/master/api-keys.html
10:11:43 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/enterprise-search-clients/php/8.2/connecting.html contains broken links to:
10:11:43 INFO:build_docs:   - en/kibana/master/api-keys.html
10:11:43 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/enterprise-search-clients/php/8.3/connecting.html contains broken links to:
10:11:43 INFO:build_docs:   - en/kibana/master/api-keys.html
10:11:43 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/enterprise-search-clients/php/8.4/connecting.html contains broken links to:
10:11:43 INFO:build_docs:   - en/kibana/master/api-keys.html
10:11:43 INFO:build_docs:  /tmp/docsbuild/target_repo/html/en/enterprise-search-clients/php/current/connecting.html contains broken links to:
10:11:43 INFO:build_docs:   - en/kibana/master/api-keys.html

[chriscressman]

@ezimuel Are you OK with me merging this PR and backporting the commit to other branches?

To avoid issues when master changes to main, I need to backport this commit to the following branches:

• 8.4
• 8.3
• 8.2
• 8.1
• 8.0
• 7.17
• 7.16

If it's OK with you, I'll merge this PR and then cherry-pick the commit to each of these branches.

[chriscressman]

I completed the backports. The change applied to 8.x only, so I cherry-pick the commit to 8.0 through 8.5.

[ezimuel]

Thanks @chriscressman. In the meantime I renamed master to main for enterprise-search-php.