chore(deps): update dependency semantic-release to v21

Author: renovate[bot]

package.json

@@ -15,7 +15,7 @@
     "@commitlint/config-conventional": "^7.1.2",
     "@commitlint/travis-cli": "^7.2.1",
     "husky": "^1.1.3",
-    "semantic-release": "^15.10.8",
+    "semantic-release": "^21.0.0",
     "travis-deploy-once": "^5.0.9"
   },
   "renovate-config": {