Remove the globals dependency

This dependency got introduced in PR mozilla#10293, almost six years ago now,
because `eslint-plugin-mozilla` didn't work without it but also didn't
require it as a dependency itself.

However, nowadays `eslint-plugin-mozilla` works just fine without it,
and other dependencies that need it correctly require it themselves.
This can be seen using `npm ls globals`:

```
$ npm ls globals
pdf.js
├─┬ @babel/[email protected]
│ └─┬ @babel/[email protected]
│   └── [email protected]
├─┬ @babel/[email protected]
│ └─┬ @babel/[email protected]
│   └── [email protected]
├─┬ [email protected]
│ └── [email protected] deduped
├─┬ [email protected]
│ ├─┬ @eslint/[email protected]
│ │ └── [email protected]
│ └── [email protected]
└── [email protected]
```

Further proof that `eslint-plugin-mozilla` (no longer) uses `globals` is
from a source code search in
https://searchfox.org/mozilla-central/search?q=globals&path=&case=false&regexp=false.
The only results for `eslint-plugin-mozilla` refer to a file named
`globals.js`, but the `globals` NPM package is not actually imported
anywhere.

Given this we should be able to safely get rid of this explicit
dependency on our end now.

package.json

@@ -28,7 +28,6 @@
     "eslint-plugin-prettier": "^5.2.1",
     "eslint-plugin-sort-exports": "^0.9.1",
     "eslint-plugin-unicorn": "^55.0.0",
-    "globals": "^15.8.0",
     "gulp": "^5.0.0",
     "gulp-cli": "^3.0.0",
     "gulp-postcss": "^10.0.0",