Remove replica selection change FF for LB [RUN ALL RSPEC] [RUN AS-IF-FOSS]

What does this MR do?

Removes the feature flag: sidekiq_load_balancing_rotate_up_to_date_replica.

Screenshots (strongly suggested)

We see fewer retries as the result of this change.
The red line on the screenshot is when the feature flag was enabled for 100%.
This may be a statistical fluctuation, but it's very important that it didn't become worse.
We should see an even better picture in the long run (1 week+).

Does this MR meet the acceptance criteria?

Conformity

• I have included changelog trailers, or none are needed. (Does this MR need a changelog?)
• I have added/updated documentation, or it's not needed. (Is documentation required?)
• I have properly separated EE content from FOSS, or this MR is FOSS only. (Where should EE code go?)
• [s] I have added information for database reviewers in the MR description, or it's not needed. (Does this MR have database related changes?)
• I have self-reviewed this MR per code review guidelines.
• This MR does not harm performance, or I have asked a reviewer to help assess the performance impact. (Merge request performance guidelines)
• I have followed the style guides.
• This change is backwards compatible across updates, or this does not apply.

Availability and Testing

• I have added/updated tests following the Testing Guide, or it's not needed. (Consider all test levels. See the Test Planning Process.)
• I have tested this MR in all supported browsers, or it's not needed.
• I have informed the Infrastructure department of a default or new setting change per definition of done, or it's not needed.

Security

N/A

Related to #333153 (closed)