Fix visiting RPM files

Fix visiting RPM files

We cannot call 'sh-set-shell' inside 'sh-base-mode', since various
settings of 'sh-mode', in particular the syntax table, is not yet
set.  Likewise with various hooks: since 'sh-base-mode' is not a
mode any file should be visited with, it makes no sense to set up
stuff like 'hack-local-variables-hook' in 'sh-base-mode'; it
should be set in the descendant modes instead.
* lisp/progmodes/sh-script.el (sh-base-mode): Move the call to
'sh-set-shell' from here...
(sh-mode): ...to here...
(bash-ts-mode): ...with a copy here.  (Bug#62748)