ci: Add clean on re-run to lint workflow

.github/workflows/lint.yml

@@ -41,6 +41,13 @@ jobs:
             ${{ runner.os }}-mix-${{ env.cache-name }}-
             ${{ runner.os }}-mix-
 
+      - name: Clean dependencies to rule out incremental build as source of failures
+        if: github.run_attempt != '1'
+        run: |
+          mix deps.clean --all
+          mix clean
+        shell: sh
+
       - name: Install dependencies
         run: mix deps.get