fix: add VERSION to env in publish.yaml

[jsjoeio]

When I did the last release, VERSION wasn't defined which lead to a
blank string in the PR title and the commit message here:

coder/code-server-aur#24

This should fix that.

[codecov]

Codecov Report

Merging #5868 (0421607) into main (48588ee) will not change coverage.
The diff coverage is n/a.

Additional details and impacted files

@@           Coverage Diff           @@
##             main    #5868   +/-   ##
=======================================
  Coverage   74.94%   74.94%           
=======================================
  Files          30       30           
  Lines        1688     1688           
  Branches      371      371           
=======================================
  Hits         1265     1265           
  Misses        361      361           
  Partials       62       62           

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[github-actions]

✨ code-server dev build published to npm for PR #5868!

• Last publish status: success
• Commit: 0421607

To install in a local project, run:

npm install @coder/code-server-pr@5868

To install globally, run:

npm install -g @coder/code-server-pr@5868