[wasm][eh] Add another hint for enabling the flag

The section might be the first EH-related part being found, and then it
makes sense to include the hint about the flag in the error message.

R=thibaudm@chromium.org

Bug: v8:8091
Change-Id: I1680090f6ff3d9496a11db51f45d990d34f234ca
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2707204Reviewed-by: Thibaud Michaud <thibaudm@chromium.org>
Commit-Queue: Clemens Backes <clemensb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#72902}

src/wasm/module-decoder.cc

@@ -505,7 +505,9 @@ class ModuleDecoderImpl : public Decoder {
         if (enabled_features_.has_eh()) {
           DecodeExceptionSection();
         } else {
-          errorf(pc(), "unexpected section <%s>", SectionName(section_code));
+          errorf(pc(),
+                 "unexpected section <%s> (enable with --experimental-wasm-eh)",
+                 SectionName(section_code));
         }
         break;
       default: