fix(deps): update dependency conventional-changelog to v3.1.21 (#586)

Co-authored-by: Renovate Bot <[email protected]>

Author: renovate[bot]

Diff for: package.json

@@ -35,7 +35,7 @@
   "homepage": "https://github.com/conventional-changelog/standard-version#readme",
   "dependencies": {
     "chalk": "2.4.2",
-    "conventional-changelog": "3.1.18",
+    "conventional-changelog": "3.1.21",
     "conventional-changelog-config-spec": "2.1.0",
     "conventional-changelog-conventionalcommits": "4.3.0",
     "conventional-recommended-bump": "6.0.9",