Currently a dependency for grape `~> 1.1` is defined but gitlab does not work…

What does this MR do?

The current version 11.5.1 depends on grape ~> 1.1 which allows an installation of grape 1.2. But gitlab does not work with grape 1.2 you see an error message if you try to execute the database migration.

This patch makes sure that grape 1.1.x is used by gitlab.

What are the relevant issue numbers?

Does this MR meet the acceptance criteria?

• Changelog entry added, if necessary
• Documentation created/updated
• Tests added for this feature/bug
• Conforms to the code review guidelines
• Conforms to the merge request performance guidelines
• Conforms to the style guides
• Conforms to the database guides
• Link to e2e tests MR added if this MR has Requires e2e tests label. See the Test Planning Process.
• Security reports checked/validated by reviewer