Fix dataclassses spelling

Doc/whatsnew/3.10.rst

@@ -996,7 +996,7 @@ Added ``slots`` parameter in :func:`dataclasses.dataclass` decorator.
 Keyword-only fields
 ~~~~~~~~~~~~~~~~~~~
 
-dataclassses now supports fields that are keyword-only in the
+dataclasses now supports fields that are keyword-only in the
 generated __init__ method.  There are a number of ways of specifying
 keyword-only fields.
 

Lib/dataclasses.py

@@ -1387,7 +1387,7 @@ def exec_body_callback(ns):
         ns['__annotations__'] = annotations
 
     # We use `types.new_class()` instead of simply `type()` to allow dynamic creation
-    # of generic dataclassses.
+    # of generic dataclasses.
     cls = types.new_class(cls_name, bases, {}, exec_body_callback)
 
     # Apply the normal decorator.

Lib/test/test_dataclasses.py

@@ -1907,7 +1907,7 @@ class Parent(Generic[T]):
         # Check MRO resolution.
         self.assertEqual(Child.__mro__, (Child, Parent, Generic, object))
 
-    def test_dataclassses_pickleable(self):
+    def test_dataclasses_pickleable(self):
         global P, Q, R
         @dataclass
         class P: