pythongh-106392: Fix consistency in pydatetime error messages

Previously python#106436 fixed consistency within the suggested replacement,
but not in the entire message

Author: hauntsaninja

Lib/_pydatetime.py

@@ -1809,7 +1809,7 @@ def fromtimestamp(cls, timestamp, tz=None):
     def utcfromtimestamp(cls, t):
         """Construct a naive UTC datetime from a POSIX timestamp."""
         import warnings
-        warnings.warn("datetime.utcfromtimestamp() is deprecated and scheduled "
+        warnings.warn("datetime.datetime.utcfromtimestamp() is deprecated and scheduled "
                       "for removal in a future version. Use timezone-aware "
                       "objects to represent datetimes in UTC: "
                       "datetime.datetime.fromtimestamp(t, datetime.UTC).",
@@ -1827,8 +1827,8 @@ def now(cls, tz=None):
     def utcnow(cls):
         "Construct a UTC datetime from time.time()."
         import warnings
-        warnings.warn("datetime.utcnow() is deprecated and scheduled for "
-                      "removal in a future version. Instead, Use timezone-aware "
+        warnings.warn("datetime.datetime.utcnow() is deprecated and scheduled for "
+                      "removal in a future version. Use timezone-aware "
                       "objects to represent datetimes in UTC: "
                       "datetime.datetime.now(datetime.UTC).",
                       DeprecationWarning,