chore(deps): update dependency sinon to v21 (googleapis#3683)

Co-authored-by: sofisl <[email protected]>

Author: renovate-bot

.github/scripts/package.json

@@ -16,6 +16,6 @@
     "devDependencies": {
         "@octokit/rest": "^19.0.0",
         "mocha": "^10.0.0",
-        "sinon": "^18.0.0"
+        "sinon": "^21.0.0"
     }
 }

package.json

@@ -95,7 +95,7 @@
     "proxyquire": "^2.1.3",
     "rimraf": "^5.0.0",
     "server-destroy": "^1.0.1",
-    "sinon": "^20.0.0",
+    "sinon": "^21.0.0",
     "tmp": "^0.2.3",
     "typescript": "^5.8.3",
     "yargs-parser": "^21.1.1"