Upgrade jQuery to 3.5.0, remove jQuery-Migrate, fix deprecations (#11055)

- Removed jQuery-Migrate as it seems to no longer be needed.
- Removed a dead code section.
- Fixed some deprecations detected by jQuery-Migrate.

Ref: https://jquery.com/upgrade-guide/3.5/
Ref: https://github.com/gogs/gogs/search?q=repo-name-change-prompt
Ref: https://github.com/go-gitea/gitea/search?q=repo-name-change-prompt
Fixes: https://github.com/go-gitea/gitea/issues/9372

Co-authored-by: zeripath <art27@cantab.net>

package-lock.json

@@ -7861,9 +7861,9 @@
       }
     },
     "jquery": {
-      "version": "3.4.1",
-      "resolved": "https://registry.npmjs.org/jquery/-/jquery-3.4.1.tgz",
-      "integrity": "sha512-36+AdBzCL+y6qjw5Tx7HgzeGCzC81MDDgaUP8ld2zhx58HdqXGoBd+tHdrBMiyjGQs0Hxs/MLZTu/eHNJJuWPw=="
+      "version": "3.5.0",
+      "resolved": "https://registry.npmjs.org/jquery/-/jquery-3.5.0.tgz",
+      "integrity": "sha512-Xb7SVYMvygPxbFMpTFQiHh1J7HClEaThguL15N/Gg37Lri/qKyhRGZYzHRyLH8Stq3Aow0LsHO2O2ci86fCrNQ=="
     },
     "jquery-datetimepicker": {
       "version": "2.5.21",
@@ -7875,11 +7875,6 @@
         "php-date-formatter": "^1.3.4"
       }
     },
-    "jquery-migrate": {
-      "version": "3.1.0",
-      "resolved": "https://registry.npmjs.org/jquery-migrate/-/jquery-migrate-3.1.0.tgz",
-      "integrity": "sha512-u/MtE1ST2pCr3rCyouJG2xMiw/k3OzLNeRKprjKTeHUezCGr0DyEgeXFdqFLmQfxfR5EsVu+mGo/sCcYdiYcIQ=="
-    },
     "jquery-mousewheel": {
       "version": "3.1.13",
       "resolved": "https://registry.npmjs.org/jquery-mousewheel/-/jquery-mousewheel-3.1.13.tgz",