Fix docstring typo.
diff --git a/Lib/decimal.py b/Lib/decimal.py
index d8abf55..5d25012 100644
--- a/Lib/decimal.py
+++ b/Lib/decimal.py
@@ -3456,7 +3456,7 @@
 
     # PEP 3101 support.  See also _parse_format_specifier and _format_align
     def __format__(self, specifier, context=None):
-        """Format a Decimal class according to the given specifier.
+        """Format a Decimal instance according to the given specifier.
 
         The specifier should be a standard format specifier, with the
         form described in PEP 3101.  Formatting types 'e', 'E', 'f',