Wrapper script sets `PATH` when running `cylc hub` which breaks version selection for `cylc play` in UI

[MetRonnie]

This prevents users choosing a version of Cylc to play a workflow with in the UI, as the cylc command from CYLC_HOME takes precedence

https://github.com/cylc/cylc-flow/blob/1dace6e30dd029d4e31098e7386cc0550ff680b3/cylc/flow/etc/cylc#L175-L178

[oliver-sanders]

Make sure to add a cylc-doc changes entry for this so we announce it on Discourse as sites will need to edit their deployments.