tests: Move CPy diff test to real test now that subclass equality works.

Testing for equality of subclassed strings now works, thanks to commit
3aab54bf43

tests/basics/subclass_native_str.py

@@ -0,0 +1,10 @@
+# Test subclassing built-in str
+
+class S(str):
+    pass
+
+s = S('hello')
+print(s == 'hello')
+print('hello' == s)
+print(s == 'Hello')
+print('Hello' == s)

tests/cpydiff/types_str_subclassequality.py

@@ -1,11 +0,0 @@
-"""
-categories: Types,str
-description: Instance of a subclass of str cannot be compared for equality with an instance of a str
-cause: Unknown
-workaround: Unknown
-"""
-class S(str):
-    pass
-
-s = S('hello')
-print(s == 'hello')