[regexp] Fix assert about unicode in experimental engine

Follow up to 3f4f4a0d: "[regexp] Handle zero-length matches in
experimental engine".

We want to assert an equivalence, not an implication in the boring
direction.

Bug: v8:10765
Change-Id: Ia7b4851feb1f5f621d687779d0cae0e28433f00e
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/2398536Reviewed-by: Jakob Gruber <jgruber@chromium.org>
Commit-Queue: Martin Bidlingmaier <mbid@google.com>
Cr-Commit-Position: refs/heads/master@{#69764}

src/regexp/experimental/experimental-compiler.cc

@@ -36,8 +36,9 @@ class CanBeHandledVisitor final : private RegExpVisitor {
     // TODO(mbid, v8:10765): We should be able to support all flags in the
     // future.
     static constexpr JSRegExp::Flags kAllowedFlags = JSRegExp::kGlobal;
-    STATIC_ASSERT(!ExperimentalRegExp::kSupportsUnicode ||
-                  (kAllowedFlags & JSRegExp::kUnicode) == 0);
+    // We support Unicode iff kUnicode is among the supported flags.
+    STATIC_ASSERT(ExperimentalRegExp::kSupportsUnicode ==
+                  ((kAllowedFlags & JSRegExp::kUnicode) != 0));
     return (flags & ~kAllowedFlags) == 0;
   }