ci: Fix a GitHub warning about Grunt < 1.3.0

Author: Raphaël Droz

package.json

@@ -43,7 +43,7 @@
     "@rollup/plugin-node-resolve": "^11.1.0",
     "@rollup/plugin-replace": "^2.3.4",
     "core-js": "^3.8.3",
-    "grunt": "1.3.0",
+    "grunt": ">=1.3.0",
     "grunt-bump": "0.8.0",
     "grunt-contrib-clean": "2.0.0",
     "grunt-contrib-copy": "1.0.0",