Revert "Add support for upcoming ppx_base. (#541)"

This reverts commit 032cb62af6.

src/gen_rules.ml

@@ -1021,11 +1021,7 @@ module Gen(P : Params) = struct
           if List.exists deps ~f:(function
             | "ppx_driver" | "ppx_type_conv" -> true
             | _ -> false) then
-            pps @ [match Scope.name scope with
-              | Some "ppx_base" ->
-                Pp.of_string "ppx_base.runner"
-              | _ ->
-                Pp.of_string "ppx_driver.runner"]
+            pps @ [Pp.of_string "ppx_driver.runner"]
           else
             pps
         in

src/super_context.ml

@@ -953,7 +953,7 @@ module PP = struct
 
   let uses_ppx_driver ~pps =
     match Option.map ~f:Pp.to_string (List.last pps) with
-    | Some ("ppx_driver.runner" | "ppx_base.runner") -> true
+    | Some "ppx_driver.runner" -> true
     | Some _ | None -> false
 
   let promote_correction ~uses_ppx_driver fn build =