[3.14] Use subcommand over sub-command in argparse docs (GH-142488) (#142587)

Use subcommand over sub-command in argparse docs (GH-142488) (cherry picked from commit 387f88c) Co-authored-by: Savannah Ostrowski <savannah@python.org>

Author: miss-islington

Doc/library/argparse.rst

@@ -1669,7 +1669,7 @@ The Namespace object
 Other utilities
 ---------------
 
-Sub-commands
+Subcommands
 ^^^^^^^^^^^^
 
 .. method:: ArgumentParser.add_subparsers(*, [title], [description], [prog], \
@@ -1698,7 +1698,7 @@ Sub-commands
  * *description* - description for the sub-parser group in help output, by
  default ``None``
 
- * *prog* - usage information that will be displayed with sub-command help,
+ * *prog* - usage information that will be displayed with subcommand help,
  by default the name of the program and any positional arguments before the
  subparser argument
 
@@ -1708,7 +1708,7 @@ Sub-commands
  * action_ - the basic type of action to be taken when this argument is
  encountered at the command line
 
- * dest_ - name of the attribute under which sub-command name will be
+ * dest_ - name of the attribute under which subcommand name will be
  stored; by default ``None`` and no value is stored
 
  * required_ - Whether or not a subcommand must be provided, by default