Fix typo in Standard Library Types documentation

Backport of: #12565

Author: WEGFan

docs/api/standard_library_types.md

@@ -266,7 +266,7 @@ Standard library type: [`enum.IntEnum`][].
 <h4>Validation</h4>
 
 * If the [`enum.IntEnum`][] type is used directly, any [`enum.IntEnum`][] instance is validated as-is
-* Id an [`enum.IntEnum`][] subclass is used as a type, any enum member or value that correspond to the
+* If an [`enum.IntEnum`][] subclass is used as a type, any enum member or value that correspond to the
   enum members values is validated as-is.
 
 See [Enums](#enums) for more details.
@@ -692,7 +692,7 @@ Standard library type: [`enum.Enum`][].
 <h3>Validation</h3>
 
 * If the [`enum.Enum`][] type is used directly, any [`enum.Enum`][] instance is validated as-is.
-* Id an [`enum.Enum`][] subclass is used as a type, any enum member or value that correspond to the
+* If an [`enum.Enum`][] subclass is used as a type, any enum member or value that correspond to the
   enum members [values][enum.Enum.value] is validated as-is.
 
 <h3>Serialization</h3>