Historically, systemd-tmpfiles was designed to manager temporary
files, but nowadays it has become a generic tool for managing
all kinds of files. To avoid user confusion, let's remove "temporary"
from the tool's description.
As discussed in #33349
This makes things a bit simpler and the build a bit faster, because we don't
have to rewrite files to do the trivial substitution. @rootbindir@ is always in
our internal $PATH that we use for non-absolute paths, so there should be no
functional change.
