Revert "Add 15s timeout to GitLab UrlBlocker"

What does this MR do?

This MR reverts !52895 (diffs) (cc @hchouraria @robotmay_gitlab @splattael )

Per the discussion in #11951 (comment 510493804) , this was causing some odd segfaults (resolved via !54404 (merged) ) and the functionality it depends on is being removed in ruby 3: https://github.com/ruby/ruby/commit/5d8bcc4870601ab1ee05346346f241d4a805aac9 .

We also have gitlab-com/gl-infra/scalability#562 (comment 488853953) -> https://bugs.ruby-lang.org/issues/17561

Best to go another route with this.

Does this MR meet the acceptance criteria?

Conformity

• [-] Changelog entry
• [-] Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
• Database guides
• Separation of EE specific content

Availability and Testing

• Review and add/update tests for this feature/bug. Consider all test levels. See the Test Planning Process.
• Tested in all supported browsers
• Informed Infrastructure department of a default or new setting change, if applicable per definition of done

Security

If this MR contains changes to processing or storing of credentials or tokens, authorization and authentication methods and other items described in the security review guidelines:

• Label as security and @ mention @gitlab-com/gl-security/appsec
• The MR includes necessary changes to maintain consistency between UI, API, email, or other methods
• Security reports checked/validated by a reviewer from the AppSec team