Remove ActiveRecord patch to ignore limit on text columns

What does this MR do?

Remove ActiveRecord patch to ignore limit on text columns

This was fixed upstream in https://github.com/rails/rails/pull/8276,
in Rails 3.2.13 (Mar 18, 2013).

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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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