flux-jobs: set id.f58 as default jobid encoding

Change the default flux-jobs output format to use id.f58 instead of
just id. This results in JOBIDs taking up less horizontal space in
the default output - 12 columns instead of 20.

src/cmd/flux-jobs.py

@@ -655,7 +655,7 @@ def main():
         fmt = args.format
     else:
         fmt = (
-            "{id:>18} {username:<8.8} {name:<10.10} {status_abbrev:>6.6} "
+            "{id.f58:>12} {username:<8.8} {name:<10.10} {status_abbrev:>6.6} "
             "{ntasks:>6} {nnodes:>6h} {runtime!F:>8h} "
             "{ranks:h}"
         )