package/bash: fix naming of target-finalize-hook

When the target-finalize-hook for bash was added in commit
311c9eeb in order to write bash into
/etc/shells, it was done at the same time as for package/mksh and it was
incorrectly copied and MKSH still appeared in the name of the hook.

The hook is now correctly named BASH_ADD_BASH_TO_SHELLS

Signed-off-by: Sebastian Weyer <sebastian.weyer@smile.fr>
Signed-off-by: Peter Korsgaard <peter@korsgaard.com>