[cleanup] Remove unused function declaration

Bug: v8:8562
Change-Id: I1ad6d2febc9327e2ef93f0409f6fddf1cebb4834
Reviewed-on: https://chromium-review.googlesource.com/c/1494012
Reviewed-by: Dan Elphick <delphick@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Commit-Queue: Maciej Goszczycki <goszczycki@google.com>
Cr-Commit-Position: refs/heads/master@{#59945}

src/snapshot/snapshot.h

@@ -67,7 +67,6 @@ class Snapshot : public AllStatic {
   // ---------------- Helper methods ----------------
 
   static bool HasContextSnapshot(Isolate* isolate, size_t index);
-  static bool EmbedsScript(Isolate* isolate);
 
   // To be implemented by the snapshot source.
   static const v8::StartupData* DefaultSnapshotBlob();