Remove bash -c prefix for pg_dump command

need to keep the `sudo -u postgres pg_dump ..` part as simple as
possible, since must declare `sudoers` allowance for that

rattail_fabric2/postgresql.py

@@ -28,7 +28,6 @@ import os
 import re
 
 from rattail_fabric2 import apt, append, contains, sed, uncomment
-from rattail.util import shlex_join
 
 
 def install(c):
@@ -224,7 +223,6 @@ def dump_db(c, name, port=None, exclude_tables=None,
     if skip_raw_file:
         tmp_name = f'/tmp/{gz_name}'
         cmd = f'{cmd} | gzip -c > {tmp_name}'
-        cmd = shlex_join(['bash', '-c', cmd])
         c.sudo(cmd, user='postgres')
         # TODO: should remove this file
         c.run(f"cp {tmp_name} {gz_name}")