[wasm] Fix --trace-wasm-decoder implication

--trace-wasm-decoder should not imply --single-threaded, as
--single-threaded implies --no-liftoff. Hence we cannot trace the
decoder in Liftoff mode.

R=thibaudm@chromium.org

Change-Id: I3e4f0ea119288ef88c4b00dd2f2a11244b77c204
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2287492Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#68741}

src/flags/flag-definitions.h

@@ -732,7 +732,6 @@ DEFINE_BOOL(wasm_tier_up, true,
             "enable tier up to the optimizing compiler (requires --liftoff to "
             "have an effect)")
 DEFINE_DEBUG_BOOL(trace_wasm_decoder, false, "trace decoding of wasm code")
-DEFINE_IMPLICATION(trace_wasm_decoder, single_threaded)
 DEFINE_DEBUG_BOOL(trace_wasm_compiler, false, "trace compiling of wasm code")
 DEFINE_DEBUG_BOOL(trace_wasm_interpreter, false,
                   "trace interpretation of wasm code")