Remove manual Z3 pre-download, now handled by proof-action

The action's run-audit.sh now pre-downloads solvers before audit.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: buger

.github/workflows/reqproof.yml

@@ -37,11 +37,6 @@ jobs:
           restore-keys: |
             proof-index-${{ runner.os }}-
 
-      # Pre-download Z3 solver so audit checks can use it.
-      # proof auto-downloads during verify but audit checks need it upfront.
-      - name: Pre-download Z3 solver
-        run: proof verify-properties specs/system parser --timeout 30 || echo "Z3 pre-download completed (verification may have partial results)"
-
       - uses: probelabs/proof-action@v1
         with:
           fail-level: warn