Don't show argument name hints for dynamic calls.

Mark function descriptors created for dynamic calls as having
synthesized parameter names.

 #KT-21275 Fixed

compiler/frontend/src/org/jetbrains/kotlin/resolve/calls/tasks/dynamicCalls.kt

@@ -136,6 +136,7 @@ class DynamicCallableDescriptors(storageManager: StorageManager, builtIns: Kotli
                 Modality.FINAL,
                 Visibilities.PUBLIC
         )
+        functionDescriptor.setHasSynthesizedParameterNames(true)
         return functionDescriptor
     }