Bump execa from 4.0.0 to 5.1.1

Bumps [execa](https://github.com/sindresorhus/execa) from 4.0.0 to 5.1.1.
- [Release notes](https://github.com/sindresorhus/execa/releases)
- [Commits](sindresorhus/execa@v4.0.0...v5.1.1)

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

package.json

@@ -26,7 +26,7 @@
     "babel-minify": "^0.5.1",
     "bunyan": "^1.8.12",
     "dateformat": "^3.0.3",
-    "execa": "^4.0.0",
+    "execa": "^5.1.1",
     "gunzip-file": "^0.1.1",
     "human-number": "^1.0.5",
     "ioredis": "^4.16.2",