fix: WebFrameMain mojo pipe not reset (#30630)

Co-authored-by: Samuel Maddock <samuel.maddock@gmail.com>

shell/browser/api/electron_api_web_frame_main.cc

@@ -80,6 +80,7 @@ void WebFrameMain::UpdateRenderFrameHost(content::RenderFrameHost* rfh) {
   // Should only be called when swapping frames.
   DCHECK(render_frame_);
   render_frame_ = rfh;
+  renderer_api_.reset();
 }
 
 bool WebFrameMain::CheckRenderFrame() const {