Bump gulp-imagemin from 6.2.0 to 7.1.0

Bumps [gulp-imagemin](https://github.com/sindresorhus/gulp-imagemin) from 6.2.0 to 7.1.0.
- [Release notes](https://github.com/sindresorhus/gulp-imagemin/releases)
- [Commits](https://github.com/sindresorhus/gulp-imagemin/compare/v6.2.0...v7.1.0)

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

package.json

@@ -24,7 +24,7 @@
     "gulp-babel": "^8.0.0",
     "gulp-clean-css": "^4.2.0",
     "gulp-concat": "^2.6.1",
-    "gulp-imagemin": "^6.0.0",
+    "gulp-imagemin": "^7.1.0",
     "gulp-notify": "^3.2.0",
     "gulp-postcss": "^8.0.0",
     "gulp-rename": "^1.4.0",