[wasm] Remove dead field

The {locals_names} in {WasmDebugInfo} was left unused after
https://crrev.com/c/2002541. All uses and even all accessors are removed
already.

R=thibaudm@chromium.org

Bug: v8:10019
Change-Id: Ib7ce61cf8c6a749b0919a8a6857664e2ab354785
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2011101Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65891}

src/wasm/wasm-objects.tq

@@ -45,7 +45,6 @@ extern class WasmDebugInfo extends Struct {
   instance: WasmInstanceObject;
   interpreter_handle: Foreign|Undefined;
   interpreter_reference_stack: Cell;
-  locals_names: FixedArray|Undefined;
   c_wasm_entries: FixedArray|Undefined;
   c_wasm_entry_map: Foreign|Undefined;  // Managed<wasm::SignatureMap>
 }