Upgrade js-yaml to 4.0

The only code change is switching `safeLoad` (which was removed) for `load` (which is "safe" by default now)

https://github.com/nodeca/js-yaml/blob/master/CHANGELOG.md#400---2021-01-03

package.json

@@ -24,7 +24,7 @@
   "dependencies": {
     "@actions/core": "^1.2.4",
     "@actions/github": "^2.2.0",
-    "js-yaml": "^3.13.1",
+    "js-yaml": "^4.1.0",
     "minimatch": "^3.0.4",
     "semver": "^6.1.1"
   },
@@ -33,7 +33,7 @@
     "@types/node": "^12.0.4",
     "@types/semver": "^6.0.0",
     "@types/minimatch": "^3.0.0",
-    "@types/js-yaml": "^3.12.1",
+    "@types/js-yaml": "^4.0.1",
     "@vercel/ncc": "^0.23.0",
     "jest": "^27.0.4",
     "prettier": "^2.3.0",