Simplify tests of the types of descriptor access

Author: cpennington

test-data/unit/check-classes.test

@@ -831,9 +831,7 @@ class A:
     @property
     def f(self) -> str: pass
 a = A() # type: A
-s = ''  # type: str
-s = a.f
-a = a.f  # E: Incompatible types in assignment (expression has type "str", variable has type "A")
+reveal_type(a.f)  # E: Revealed type is 'builtins.str'
 [builtins fixtures/property.pyi]
 
 [case testAssigningToReadOnlyProperty]
@@ -910,9 +908,7 @@ class A:
     f = D()
 
 a = A() # type: A
-s = ''  # type: str
-s = a.f
-a = a.f  # E: Incompatible types in assignment (expression has type "str", variable has type "A")
+reveal_type(a.f)  # E: Revealed type is 'builtins.str'
 
 [case testSettingDataDescriptor]
 import typing