We no longer quantify over an entirely-unused existential type variable

testsuite/tests/rename/should_fail/rnfail055.stderr

@@ -88,7 +88,7 @@ RnFail055.hs-boot:25:6:
     Boot file:   data T7 a
                      No C type associated
                      RecFlag NonRecursive, Promotable
-                     = T7 :: forall a b. a -> T7 a Stricts: _
+                     = T7 :: forall a. a -> T7 a Stricts: _
                      FamilyInstance: none
 
 RnFail055.hs-boot:27:22:

testsuite/tests/typecheck/should_fail/T3468.stderr

@@ -4,7 +4,7 @@ T3468.hs-boot:3:6:
     Main module: data Tool d
                      No C type associated
                      RecFlag Recursive, Promotable
-                     = F :: forall d a r. a -> Tool d Stricts: _
+                     = F :: forall d a. a -> Tool d Stricts: _
                      FamilyInstance: none
     Boot file:   abstract(False) Tool
                      No C type associated