Bump execa from 2.1.0 to 4.1.0 (#128)

Bumps [execa](https://github.com/sindresorhus/execa) from 2.1.0 to 4.1.0.
- [Release notes](https://github.com/sindresorhus/execa/releases)
- [Commits](sindresorhus/execa@v2.1.0...v4.1.0)

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

Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

package.json

@@ -54,7 +54,7 @@
   },
   "devDependencies": {
     "ava": "^3.8.1",
-    "execa": "^2.0.4",
+    "execa": "^4.1.0",
     "husky": "^4.3.0",
     "tap-growl": "^3.0.0",
     "test-rule-package": "./test/custom-rules/test-rule-package",