Fix Gitpod gems

What does this MR do?

After we upgraded ruby to 2.7.2 in the GDK, the Gitpod configuration did not work anymore. After some debugging with the amazing help of @stanhu, we figured out that the script in the gitpod.yml did not move the rvm files to the correct place, so the changes in this MR fix that.

/cc @corneliusludmann @ashmckenzie

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
• Documentation (if required)
• Code review guidelines
• Merge request performance guidelines
• Style guides
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• 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

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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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