Remove is_long from cbi-tree --prune option

Although --prune is a "long option", that's not what the "long" in
"is_long" refers to. Because --prune doesn't have a shorthand and
doesn't accept an argument, the description of the option is not
long enough to generate an initial newline.

Signed-off-by: John Pennycook <[email protected]>

Author: Pennycook

codebasin/tree.py

@@ -69,7 +69,6 @@ def _build_parser() -> argparse.ArgumentParser:
         action="store_true",
         help=_help_string(
             "Prune unused files from the tree.",
-            is_long=True,
         ),
     )
     parser.add_argument(