fix(emacs): fix tests on Emacs 27

use-package broke on Emacs 27 [1], breaking our Emacs plugin test script:

```
  INFO     Scraping files for track-changes-autoloads.el...
track-changes-pkg.el:0:0: error: void-function: (lisp-data-mode)
```

Apply a workaround to keep our CI (which uses Emacs 27) green.

[1] jwiegley/use-package#1083

Author: strager

plugin/emacs/test/quicklintjs-test.el

@@ -5,6 +5,14 @@
 (require 'ert)
 (require 'package)
 
+; https://github.com/jwiegley/use-package/issues/1083#issuecomment-2735175731
+(unless (or (fboundp 'lisp-data-mode)
+            (not enable-local-variables))
+  ;; Work around the fact that transient's autogenerated package header declares mode:
+  ;; lisp-data, which is only present in Emacs 28+, thus breaking the loading of deps
+  (message "Old Emacs version, remapping lisp-data-mode")
+  (defalias 'lisp-data-mode 'emacs-lisp-mode))
+
 (defconst cache-dir-name (concat
                           (expand-file-name default-directory)
                           ".melpa-cache/"))