fix(mr update): edge case for creation and deletion of multiple draft prefixes

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Description

Before this change running glab mr update --draft for MR with title Draft: dupa resulted in update to Draft: Draft: dupa now the title remains the same

Before this change running glab mr update --ready for MR with title Draft: Draft: dupa (created by the previous command) resulted in title Draft: dupa, now it gets rid of the whole array of draft/wip prefixes regardless of casing.

• fix(mr update): edge case for creation and deletion of multiple draft prefixes

Related Issues

Resolves #[issue_number]

How has this been tested?

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Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
• Documentation
• Chore (Related to CI or Packaging to platforms)
• Test gap