Remove FF `environment_last_visible_pipeline_disable_joins`"

What does this MR do and why?

Removes FF environment_last_visible_pipeline_disable_joins introduced in !68870 (merged)

It was default enabled in the config file, so we do not run chatops command for feature enabling.

Screenshots or screen recordings

These are strongly recommended to assist reviewers and reduce the time to merge your change.

How to set up and validate locally

Visiting gitlab.com/-/operations/environments and the queries should not have cross join with ci database tables.

Example: #338006 (comment 679540098)

MR acceptance checklist

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• I have evaluated the MR acceptance checklist for this MR.

Related to #340283 (closed)