patch 9.1.0675: Patch v9.1.0674 causes problems

Problem:  Patch v9.1.0674 causes problems
Solution: Revert it for now

Revert "patch 9.1.0674: Vim9: compiling abstract method fails because of missing return"

This reverts commit 7477861e0d.

Signed-off-by: Christian Brabandt <cb@256bit.org>

src/testdir/test_vim9_class.vim

@@ -6264,27 +6264,6 @@ def Test_abstract_method()
     assert_equal('foo', A.Foo())
   END
   v9.CheckSourceSuccess(lines)
-
-  # Invoke method returning a value through the abstract class. See #15432.
-  lines =<< trim END
-    vim9script
-
-    abstract class A
-        abstract def String(): string
-    endclass
-
-    class B extends A
-        def String(): string
-            return 'B'
-        enddef
-    endclass
-
-    def F(o: A)
-        assert_equal('B', o.String())
-    enddef
-    F(B.new())
-  END
-  v9.CheckSourceSuccess(lines)
 enddef
 
 " Test for calling a class method from a subclass