Fix minor docstring issues in `dataclasses.py`. (gh-93024)

Previously, when using `functools.wrap` around them (and inherit their docstrings), sphinx renders the docstrings badly and raises warnings about wrong indent.

Lib/dataclasses.py

@@ -1255,7 +1255,7 @@ def asdict(obj, *, dict_factory=dict):
     """Return the fields of a dataclass instance as a new dictionary mapping
     field names to field values.
 
-    Example usage:
+    Example usage::
 
       @dataclass
       class C:
@@ -1326,8 +1326,8 @@ def astuple(obj, *, tuple_factory=tuple):
           x: int
           y: int
 
-    c = C(1, 2)
-    assert astuple(c) == (1, 2)
+      c = C(1, 2)
+      assert astuple(c) == (1, 2)
 
     If given, 'tuple_factory' will be used instead of built-in tuple.
     The function applies recursively to field values that are
@@ -1376,11 +1376,11 @@ def make_dataclass(cls_name, fields, *, bases=(), namespace=None, init=True,
     The dataclass name will be 'cls_name'.  'fields' is an iterable
     of either (name), (name, type) or (name, type, Field) objects. If type is
     omitted, use the string 'typing.Any'.  Field objects are created by
-    the equivalent of calling 'field(name, type [, Field-info])'.
+    the equivalent of calling 'field(name, type [, Field-info])'.::
 
       C = make_dataclass('C', ['x', ('y', int), ('z', int, field(init=False))], bases=(Base,))
 
-    is equivalent to:
+    is equivalent to::
 
       @dataclass
       class C(Base):
@@ -1444,7 +1444,7 @@ def make_dataclass(cls_name, fields, *, bases=(), namespace=None, init=True,
 def replace(obj, /, **changes):
     """Return a new object replacing specified fields with new values.
 
-    This is especially useful for frozen classes.  Example usage:
+    This is especially useful for frozen classes.  Example usage::
 
       @dataclass(frozen=True)
       class C:
@@ -1454,7 +1454,7 @@ def replace(obj, /, **changes):
       c = C(1, 2)
       c1 = replace(c, x=3)
       assert c1.x == 3 and c1.y == 2
-      """
+    """
 
     # We're going to mutate 'changes', but that's okay because it's a
     # new dict, even if called with 'replace(obj, **my_changes)'.