Explicitly add erubi to Gemfile and unquarantine elasticsearch_reindexing_spec test

What does this MR do?

It seems the error "14:failed to connect to all addresses"],"limit_reached" was caused by gitaly failing to have its dependency erubi installed. I've added it to the Gemfile and Gemfile.lock here.

To verify that this fix works I've examined the gitaly "current" logs before the change and after. The logs after show no errors pertaining to the bootstrap process that were present before the change.

closes #197207 (closed) closes #199911 (closed)

current_gitaly_logs_pre_change_

current_gitaly_logs_post_change_

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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

Security

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• 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
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