Monkeypatch: in CodeMirror, revert less.js to a working version

[njx]

For #6057, this hotfixes the CodeMirror submodule to point to a temporary branch (also named post-sprint-34-hotfix) that reverts the LESS mode to codemirror/codemirror5@390a47e. A bug was introduced in codemirror/codemirror5@6fd2965 that was later fixed (after our most recent upstream merge). Rather than try to take the latest upstream or monkeypatch in the bugfixes, we thought it would be safer to just revert codemirror/codemirror5@6fd2965 since it was a rather large change to the LESS mode and we probably don't need the fixes in that commit right now.

[RaymondLim]

I reviewed the changes and just found that less.js is the only file reverted to the version in sprint 33. I also tested with different less files and didn't see any issues. I will let @bchintx to decide what to do with this pull request since he has to make the corresponding change in EC.

[bchintx]

Whoops. Just saw @RaymondLim 's comment, but not until after I did the same. :-)

Verified that the updated SHA only changes the one less file, and then confirmed that issue #6057 is fixed with this change.

Merging this pull request, and then creating a new one to echo this change in Edge Code.

[pthiess]

@njx @RaymondLim @bchintx - Cool! Thanks a ton -:)

[FezVrasta]

There is a way to replace the bugged less.js in the Sprint 34 without compile it or use the git version? Thanks.

[njx]

Yes, as a workaround, you could manually copy that file over from our adobe/CodeMirror2 fork into the appropriate place in your local Brackets install (under src/thirdparty/CodeMirror2).

[FezVrasta]

Thank you very much. It worked.