Release Sector 9.4.0

Due to feedback on the lack of a 9.4.x branch being a bit confusing for users after all, we are releasing a 9.4.x branch now.

To keep things simple, there will be no further commits or releases on the 9.3.x branch and it will be deprecated by this release.

We upgraded to Drupal 9.4 previously and so are skipping our usual deprecation process for this branch (removing obsolete modules and warnings) as a compromise to not make more working during the December period.

The upgrade from 9.3.x to 9.4.x will simply change a few minor versions in core and contrib.

Deprecation/removals and new features will resume with Sector 10.

This backpedal here will also mean that a Sector 9.5.x branch and release will happen early year in line with Drupal 9.5. Again, that branch will not introduce deprecations other than instantly heralding end of support for the 9.4.x branch of Sector.

The commit to this ticket will resolve #3326653: Update block_class module.