PY-20662 Fixed: Making any magic method async displays an error, even though it is sometimes legal

Mark __call__ builtin as allowed to be async

python/src/com/jetbrains/python/psi/impl/PyFunctionImpl.java

@@ -695,7 +695,7 @@ public class PyFunctionImpl extends PyBaseElementImpl<PyFunctionStub> implements
 
     return languageLevel.isAtLeast(LanguageLevel.PYTHON35) && (
       functionName == null ||
-      ArrayUtil.contains(functionName, PyNames.AITER, PyNames.ANEXT, PyNames.AENTER, PyNames.AEXIT) ||
+      ArrayUtil.contains(functionName, PyNames.AITER, PyNames.ANEXT, PyNames.AENTER, PyNames.AEXIT, PyNames.CALL) ||
       !PyNames.getBuiltinMethods(languageLevel).containsKey(functionName)
     );
   }

python/testData/highlighting/asyncBuiltinMethods.py

@@ -6,4 +6,7 @@ class A:
         pass
 
     async def __aiter__(self):
+        pass
+
+    async def __call__(self, *args, **kwargs):
         pass