fix: remove CHECK_EQ for swapped RFH

[samuelmaddock]

Description of Change

fixes #30807

Backport a fix from #29290 which has already made it into main and 15-x-y branches.

The check below will get thrown sometimes when the old_host is a nullptr which I hadn't expected initially. The code works fine with this check removed.

electron/shell/browser/api/electron_api_web_contents.cc

Lines 1426 to 1429 in c0da647

	auto* web_frame =
	WebFrameMain::FromFrameTreeNodeId(new_host->GetFrameTreeNodeId());
	if (web_frame) {
	CHECK_EQ(web_frame->render_frame_host(), old_host);

Checklist

• PR description included and stakeholders cc'd
• npm test passes
• PR release notes describe the change in a way relevant to app developers, and are capitalized, punctuated, and past tense.

Release Notes

Notes: Fixed crash that occasionally happens when closing or opening BrowserWindows.

[release-clerk]

Release Notes Persisted

Fixed crash that occasionally happens when closing or opening BrowserWindows.

[trop]

I was unable to backport this PR to "12-x-y" cleanly;
you will need to perform this backport manually.

[trop]

I have automatically backported this PR to "13-x-y", please check out #30834

[codebytere]

Removing label for 12-x-y since this depends on #30076 which is not in 12.