docs(docstring of _in()): Use semantic newlines

Author: iron3oxide

src/attr/validators.py

@@ -330,9 +330,11 @@ def in_(options, verbose_value_error=False):
     :param verbose_value_error: Determines extent of the ValueError signature.
     :type verbose_value_error: bool
 
-    :raises ValueError: With a human readable error message, and if
-       verbose_value_error is set to True, the attribute (of type
-       `attrs.Attribute`), the expected options, and the value it got.
+    :raises ValueError: With a human readable error message,
+        and if verbose_value_error is set to True,
+        the attribute (of type `attrs.Attribute`),
+        the expected options,
+        and the value it got.
 
     .. versionadded:: 17.1.0
     """