have prober test use staging TSA (#1540)

Signed-off-by: Bob Callaway <[email protected]>

Author: bobcallaway

.github/workflows/prober-test.yml

@@ -30,4 +30,4 @@ jobs:
 
       - name: Prober test
         id: prober-test
-        run: go run ./cmd/prober --one-time --write-prober --logStyle dev
+        run: go run ./cmd/prober --one-time --write-prober --logStyle dev -tsa-url https://timestamp.sigstage.dev