Remove nested quotes

Author: anfelor

ocaml/testsuite/tests/typing-unique/overwriting_underscore.ml

@@ -11,7 +11,7 @@ let underscore () = _
 Line 1, characters 20-21:
 1 | let underscore () = _
                         ^
-Error: Syntax error: "wildcard "_"" not expected.
+Error: Syntax error: "wildcard _" not expected.
 |}]
 
 let overwriting t = overwrite_ t with (a, b)

ocaml/typing/typecore.ml

@@ -6534,7 +6534,7 @@ and type_expect_
       else Location.todo_overwrite_not_implemented loc
   | Pexp_hole ->
       if not (Language_extension.is_enabled Overwriting) then
-        raise Syntaxerr.(Error(Not_expecting(loc, "wildcard \"_\"")))
+        raise Syntaxerr.(Error(Not_expecting(loc, "wildcard _")))
       else Location.todo_overwrite_not_implemented loc
 
 and expression_constraint pexp =