[cleanup] Delete BytecodeArray functions with no impl

BytecodeArray::SourcePosition and BytecodeArray::SourceStatementPosition
have no implementations and are never called.

Bug: v8:8834
Change-Id: I919c871795084766856dfbff5344c037b6f33dd0
Reviewed-on: https://chromium-review.googlesource.com/c/1497009
Commit-Queue: Dan Elphick <delphick@chromium.org>
Commit-Queue: Ross McIlroy <rmcilroy@chromium.org>
Auto-Submit: Dan Elphick <delphick@chromium.org>
Reviewed-by: Ross McIlroy <rmcilroy@chromium.org>
Cr-Commit-Position: refs/heads/master@{#59998}

src/objects/code.h

@@ -793,9 +793,6 @@ class BytecodeArray : public FixedArrayBase {
   // bytecode, constant pool, source position table, and handler table.
   inline int SizeIncludingMetadata();
 
-  int SourcePosition(int offset);
-  int SourceStatementPosition(int offset);
-
   DECL_PRINTER(BytecodeArray)
   DECL_VERIFIER(BytecodeArray)