ci: remove start-workspace workflow (deprecated) (#21291)

This workflow is no longer used and can be removed.

Refs #21023

.github/workflows/start-workspace.yaml

@@ -1,35 +0,0 @@
-name: Start Workspace On Issue Creation or Comment
-
-on:
-  issues:
-    types: [opened]
-  issue_comment:
-    types: [created]
-
-permissions:
-  issues: write
-
-jobs:
-  comment:
-    runs-on: ubuntu-latest
-    if: >-
-      (github.event_name == 'issue_comment' && contains(github.event.comment.body, '@coder')) || 
-      (github.event_name == 'issues' && contains(github.event.issue.body, '@coder'))
-    environment: dev.coder.com
-    timeout-minutes: 5
-    steps:
-      - name: Start Coder workspace
-        uses: coder/start-workspace-action@f97a681b4cc7985c9eef9963750c7cc6ebc93a19
-        with:
-          github-token: ${{ secrets.GITHUB_TOKEN }}
-          github-username: >-
-            ${{
-              (github.event_name == 'issue_comment' && github.event.comment.user.login) || 
-              (github.event_name == 'issues' && github.event.issue.user.login)
-            }}
-          coder-url: ${{ secrets.CODER_URL }}
-          coder-token: ${{ secrets.CODER_TOKEN }}
-          template-name: ${{ secrets.CODER_TEMPLATE_NAME }}
-          parameters: |-
-            AI Prompt: "Use the gh CLI tool to read the details of issue https://github.com/${{ github.repository }}/issues/${{ github.event.issue.number }} and then address it."
-            Region: us-pittsburgh