fix[devtools/extension]: unregister dynamically injected content scripts instead of filtering (#27369)

Same as https://github.com/facebook/react/pull/26765.
Related bug report -
https://bugs.chromium.org/p/chromium/issues/detail?id=1393762.

This was changed in https://github.com/facebook/react/pull/27215, when I
have refactored background logic in the extension. I've missed this
case, because the extension was working in incognito mode.

Turns out, it stops working after the first reload, and it stops only in
incognito mode, so I am rolling out back the previous workaround.

Tested on Chrome that it fixes the extension in incognito mode and that
it doesn't affect default mode.