bpo-47105: Cite grp.h instead of pwd.h in grp docs (GH-32091) (GH-32120)

(cherry picked from commit ee912ad)

Co-authored-by: Alex Hedges <aphedges@users.noreply.github.com>

Doc/library/grp.rst

@@ -12,7 +12,7 @@ Unix versions.
 
 Group database entries are reported as a tuple-like object, whose attributes
 correspond to the members of the ``group`` structure (Attribute field below, see
-``<pwd.h>``):
+``<grp.h>``):
 
 +-------+-----------+---------------------------------+
 | Index | Attribute | Meaning                         |