Fix test to work in ocaml < 4.10

Signed-off-by: Jay Mody <[email protected]>

test/error_embedding/run.t

@@ -79,11 +79,11 @@ Error nodes are generated when dependent derivers are not applied.
 Flag `-raise-embedded-errors` raises the first embedded error in the AST.
 
   $ echo "let () = ()" > embedded_error.ml
-  $ echo "module _ = struct [%%ocaml.error \"error 1\"] end" >> embedded_error.ml
+  $ echo "module T = struct [%%ocaml.error \"error 1\"] end" >> embedded_error.ml
   $ echo "[%%ocaml.error \"error 2\"]" >> embedded_error.ml
   $ ./extender.exe embedded_error.ml -raise-embedded-errors
   File "embedded_error.ml", line 2, characters 21-32:
-  2 | module _ = struct [%%ocaml.error "error 1"] end
+  2 | module T = struct [%%ocaml.error "error 1"] end
                            ^^^^^^^^^^^
   Error: error 1
   [1]