fix: revert pre-commit change on static_viewer.html

[Jo-Byr]

Revert static_viewer.html introduced in 0d7fb06

Should fix #120

[UlysseDurand]

Maybe the .externals.sha256 file's line for the static_viewer should also be reverted
Same for the url in .fetch_externals.sh

The github workflow contains

      # -----------------------------------------------------------------------
      # Make that step a manual one and pushing files to the repo
      # -----------------------------------------------------------------------
      # - name: Install trame-vtk.js
      #   run: |
      #     bash .fetch_externals.sh
      # -----------------------------------------------------------------------

[jourdain]

So before, that fetch was automatic. Now we want to make it manual to make sure we don't brake the viewer (while still using the scripts).
Ideally, it should be integrated into the CI.

Were the url and sha updated with your edits?