typecheck/FD3: revert to error msg of previous version ofthe compiler

testsuite/tests/ghc-regress/typecheck/should_compile/FD3.hs

@@ -2,13 +2,6 @@
 
 -- Trac #1795
 
--- This should fail.  It used to fail saying it can't unify
---   'a' with '(String, a)'
--- but now it simply says that it can't deduce 
--- 	(MkA (String, a) a) from the context ()
--- which is fair enough
-
-
 module ShouldCompile where
 
 data A a = A

testsuite/tests/ghc-regress/typecheck/should_compile/FD3.stderr

-
-FD3.hs:22:14:
-    Could not deduce (MkA (String, a) a) from the context ()
-      arising from a use of `mkA' at FD3.hs:22:14-18
-    Possible fix:
-      add (MkA (String, a) a) to the context of
-	the type signature for `translate'
-      or add an instance declaration for (MkA (String, a) a)
-    In the expression: mkA a
-    In the definition of `translate': translate a = mkA a
+
+FD3.hs:15:0:
+    Occurs check: cannot construct the infinite type: a = (String, a)
+    When generalising the type(s) for `translate'