Fix "encodings" typo in argparse.FileType documentation (pythonGH-148502)

(cherry picked from commit 8ecb6b8)

Co-authored-by: Gleb Popov <gvpopov.dev@gmail.com>

Author: gleb-pp

Doc/library/argparse.rst

@@ -1828,7 +1828,7 @@ FileType objects
       Namespace(infile=<_io.TextIOWrapper name='<stdin>' encoding='UTF-8'>)
 
    .. versionchanged:: 3.4
-      Added the *encodings* and *errors* parameters.
+      Added the *encoding* and *errors* parameters.
 
 
 Argument groups