Bump gulp-exec from 4.0.0 to 5.0.0 (#231)

Bumps [gulp-exec](https://github.com/robrich/gulp-exec) from 4.0.0 to 5.0.0.
- [Release notes](https://github.com/robrich/gulp-exec/releases)
- [Commits](robrich/gulp-exec@4.0.0...5.0.0)

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

Co-authored-by: dependabot-preview[bot] <27856297+dependabot-preview[bot]@users.noreply.github.com>

Author: dependabot-preview[bot]

package.json

@@ -51,7 +51,7 @@
     "gulp-autoprefixer": "^7.0.0",
     "gulp-clean-css": "^4.0.0",
     "gulp-eslint": "^6.0.0",
-    "gulp-exec": "^4.0.0",
+    "gulp-exec": "^5.0.0",
     "gulp-header": "^2.0.5",
     "gulp-less": "^4.0.1",
     "gulp-mocha": "^7.0.0",