chore(deps-dev): bump semantic-release from 15.13.19 to 15.13.21

Bumps [semantic-release](https://github.com/semantic-release/semantic-release) from 15.13.19 to 15.13.21.
- [Release notes](https://github.com/semantic-release/semantic-release/releases)
- [Commits](semantic-release/semantic-release@v15.13.19...v15.13.21)

Signed-off-by: dependabot-preview[bot] <support@dependabot.com>

Author: dependabot-preview[bot]

package-lock.json

@@ -33,7 +33,7 @@
     "codecov": "^3.5.0",
     "mocha": "^6.2.0",
     "nyc": "^14.1.1",
-    "semantic-release": "^15.13.19",
+    "semantic-release": "^15.13.21",
     "standard": "^13.1.0"
   }
 }