remove gridstack dependency

package.json

@@ -45,7 +45,6 @@
         "core-js": "^3",
         "eslint": "^9",
         "globals": "^15",
-        "gridstack": "^7",
         "highlight.js": "^11",
         "litepicker": "^2",
         "luxon": "^3",

templates/about/license.html.twig

@@ -56,11 +56,11 @@
                         <li>Doctrine: <a href="https://www.doctrine-project.org" target="_blank">https://www.doctrine-project.org</a></li>
                         <li>FontAwesome: <a href="https://fontawesome.com" target="_blank">https://fontawesome.com</a></li>
                         <li>FullCalendar: <a href="https://fullcalendar.io" target="_blank">https://fullcalendar.io</a></li>
-                        <li>gridstack.js: <a href="https://gridstackjs.com" target="_blank">https://gridstackjs.com</a></li>
                         <li>Litepicker: <a href="https://litepicker.com/" target="_blank">https://litepicker.com/</a></li>
                         <li>Luxon: <a href="https://moment.github.io/luxon/" target="_blank">https://moment.github.io/luxon/</a></li>
                         <li>MPDF <a href="https://mpdf.github.io" target="_blank">https://mpdf.github.io</a></li>
                         <li>PHPOffice: <a href="https://github.com/PHPOffice" target="_blank">https://github.com/PHPOffice</a></li>
+                        <li>Sortable.js: <a href="https://github.com/SortableJS/Sortable" target="_blank">https://github.com/SortableJS/Sortable</a></li>
                         <li>Symfony: <a href="https://symfony.com" target="_blank">https://symfony.com</a></li>
                         <li>Tabler: <a href="https://tabler.io" target="_blank">https://tabler.io</a></li>
                         <li>Tom Select: <a href="https://tom-select.js.org/" target="_blank">https://tom-select.js.org/</a></li>

yarn.lock

@@ -3804,13 +3804,6 @@ __metadata:
   languageName: node
   linkType: hard
 
-"gridstack@npm:^7":
-  version: 7.3.0
-  resolution: "gridstack@npm:7.3.0"
-  checksum: 10/125339be00976d6d4acc709f2b3486f5a01bbf8fb90042e9a7325117f101cebcb5b12fbbc339aae6c4285a54c7e7118b865267fb586476eef81a02c40596ad69
-  languageName: node
-  linkType: hard
-
 "has-flag@npm:^3.0.0":
   version: 3.0.0
   resolution: "has-flag@npm:3.0.0"
@@ -4257,7 +4250,6 @@ __metadata:
     core-js: "npm:^3"
     eslint: "npm:^9"
     globals: "npm:^15"
-    gridstack: "npm:^7"
     highlight.js: "npm:^11"
     litepicker: "npm:^2"
     luxon: "npm:^3"