[cleanup] Remove duplicate V8DebuggerScript::setBreakpoint()

This is a bit odd, since `V8DebuggerScript::setBreakpoint()` is declared
as pure virtual in the header file, and the actual implementation is
inside the source file, in `ActualScript::setBreakpoint()`. So this is
dead code that was somehow not detected as such by the C++ compiler.

Bug: chromium:700516, chromium:1162229
Change-Id: Ifc7aa6926c21edbb0b6a5176a35711186c4958cb
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/3017801
Auto-Submit: Benedikt Meurer <bmeurer@chromium.org>
Commit-Queue: Kim-Anh Tran <kimanh@chromium.org>
Reviewed-by: Kim-Anh Tran <kimanh@chromium.org>
Cr-Commit-Position: refs/heads/master@{#75654}

src/inspector/v8-debugger-script.cc

@@ -395,12 +395,6 @@ void V8DebuggerScript::setSourceURL(const String16& sourceURL) {
   }
 }
 
-bool V8DebuggerScript::setBreakpoint(const String16& condition,
-                                     v8::debug::Location* loc, int* id) const {
-  v8::HandleScope scope(m_isolate);
-  return script()->SetBreakpoint(toV8String(m_isolate, condition), loc, id);
-}
-
 #if V8_ENABLE_WEBASSEMBLY
 void V8DebuggerScript::removeWasmBreakpoint(int id) {
   v8::HandleScope scope(m_isolate);