Clean up Ruby 3 related deprecation silences

What does this MR do?

We are moving full steam ahead with Ruby 3 support.

This means updating many of our dependencies. Until this can happen, some of the dependencies have to be added to the list of silences for deprecation_toolkit, which is a tool we use when running rspec that will fail fast with an exception if a deprecation is observed.

This MR removes 2 of these silences for which the underlying issues had been fixed already, but where we forgot to clean up the silences that were still in place:

• asciidoctor - fixed in !65528 (merged)
• gitlab-labkit - fixed in !65846 (merged)

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?)
• 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

The absence of spec failures in this MR is proof enough that these have been fixed, at least as far as code goes that is covered by tests.

For anything else we are looking to add production logging around deprecations: #333330 (closed)