fix some docstring crashes (#1593)

Allow removing some trailing whitespace

src/black/__init__.py

@@ -6063,7 +6063,7 @@ def _stringify_ast(
                 and field == "value"
                 and isinstance(value, str)
             ):
-                normalized = re.sub(r" *\n[ \t]+", "\n ", value).strip()
+                normalized = re.sub(r" *\n[ \t]*", "\n", value).strip()
             else:
                 normalized = value
             yield f"{'  ' * (depth+2)}{normalized!r},  # {value.__class__.__name__}"

tests/data/docstring.py

@@ -46,7 +46,7 @@ def zort():
 
 def poit():
   """
-  Lorem ipsum dolor sit amet.
+  Lorem ipsum dolor sit amet.       
 
   Consectetur adipiscing elit:
    - sed do eiusmod tempor incididunt ut labore
@@ -58,6 +58,14 @@ def poit():
   pass
 
 
+def under_indent():
+  """
+  These lines are indented in a way that does not
+make sense.
+  """
+  pass
+
+
 def over_indent():
   """
   This has a shallow indent
@@ -136,6 +144,14 @@ def poit():
     pass
 
 
+def under_indent():
+    """
+      These lines are indented in a way that does not
+    make sense.
+    """
+    pass
+
+
 def over_indent():
     """
     This has a shallow indent