Fix npm publish warnings about the package.json format

This commit removes the following warnings from the `npm publish` output:

```
npm warn publish npm auto-corrected some errors in your package.json when publishing.  Please run "npm pkg fix" to address these errors.
npm warn publish errors corrected:
npm warn publish Removed invalid "scripts"
npm warn publish "repository.url" was normalized to "git+https://github.com/mozilla/pdfjs-dist.git"
```

For the "scripts" section it turns out that if the package doesn't have
any scripts it's expected to explicitly set it to an empty object; refer
to npm/cli#6918 and
denoland/dnt#414.

gulpfile.mjs

@@ -2226,11 +2226,12 @@ function packageJson() {
     },
     repository: {
       type: "git",
-      url: DIST_REPO_URL,
+      url: `git+${DIST_REPO_URL}.git`,
     },
     engines: {
       node: ">=18",
     },
+    scripts: {},
   };
 
   return createStringSource(