Delete old issue template

Looks like this was forgotten...

.github/ISSUE_TEMPLATE/unitary_hack.md

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----
-name: Unitary Hack - Compilation to QIR
-about: Create a report to help us improve our new QIR generation feature!
-title: ''
-labels: 'bug, area: QIR'
-assignees: ''
----
-
-**Description of the issue**
-
-Describe briefly what this issue is that you have encountered as part of the [Unitary Hack](https://unitaryfund.github.io/unitaryhack/), and past any error messages or unexpected behavior you are seeing.
-
-**Q# code that causes the issue**
-
-Add or link the Q# code that causes the issue.
-
-**Additional context**
-
-Add any other context here that may be helpful to know.