[wasm] Remove outdated TODO

Sign extension opcodes are already tested in the interpreter since
https://crrev.com/c/1083337, thus remove the obsolete TODO.

R=gdeepti@chromium.org

No-Try: true
Change-Id: I08323b9d43fa46d1fcf9965e5106a68767f695b5
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1954400
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Reviewed-by: Deepti Gandluri <gdeepti@chromium.org>
Cr-Commit-Position: refs/heads/master@{#65364}

test/cctest/wasm/test-run-wasm-sign-extension.cc

@@ -10,7 +10,6 @@ namespace v8 {
 namespace internal {
 namespace wasm {
 
-// TODO(gdeepti): Enable tests to run in the interpreter.
 WASM_EXEC_TEST(I32SExtendI8) {
   EXPERIMENTAL_FLAG_SCOPE(se);
   WasmRunner<int32_t, int32_t> r(execution_tier);