Vendor jquery.are-you-sure with strict mode fixes (#26901)

Extract from https://github.com/go-gitea/gitea/pull/25940 and because
https://github.com/go-gitea/gitea/pull/26743 does seem to need more
work.

This will be required if we are to run our JS in [strict
mode](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Strict_mode).

Previously, the two variables `$fields` and `$dirtyForms` polluted
`window`:

<img width="1145" alt="image"
src="https://github.com/go-gitea/gitea/assets/115237/e0270a0e-b881-4ed7-9cc4-e9ab25c0a2bc">

package-lock.json

@@ -27,7 +27,6 @@
         "escape-goat": "4.0.0",
         "fast-glob": "3.3.1",
         "jquery": "3.7.1",
-        "jquery.are-you-sure": "1.9.0",
         "katex": "0.16.8",
         "license-checker-webpack-plugin": "0.2.1",
         "lightningcss-loader": "2.1.0",
@@ -6466,17 +6465,6 @@
       "resolved": "https://registry.npmjs.org/jquery/-/jquery-3.7.1.tgz",
       "integrity": "sha512-m4avr8yL8kmFN8psrbFFFmB/If14iN5o9nw/NgnnM+kybDJpRsAynV2BsfpTYrTRysYUdADVD7CkUUizgkpLfg=="
     },
-    "node_modules/jquery.are-you-sure": {
-      "version": "1.9.0",
-      "resolved": "https://registry.npmjs.org/jquery.are-you-sure/-/jquery.are-you-sure-1.9.0.tgz",
-      "integrity": "sha512-2r0uFx8CyAopjeHGOdvvwpFP921TnW1+v1uJXcAWQYHYGB1tryTDhQY+5u6HsVeMwbWiRTKVZFWnLaFpDvIqZQ==",
-      "dependencies": {
-        "jquery": ">=1.4.2"
-      },
-      "engines": {
-        "node": ">=0.8.0"
-      }
-    },
     "node_modules/js-levenshtein-esm": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/js-levenshtein-esm/-/js-levenshtein-esm-1.2.0.tgz",