Delete Research proposal.md

.gitlab/issue_templates/Research proposal.md

-### Background:
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-(Include problem, use cases, benefits, and/or goals)
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-**What questions are you trying to answer?**
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-**Are you looking to verify an existing hypothesis or uncover new issues you should be exploring?**
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-**What is the backstory of this project and how does it impact the approach?**
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-**What do you already know about the areas you are exploring?**
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-**What does success look like at the end of the project?**
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-### Links / references:
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-/label ~"UX research"