There are several `about:` pages listed in `browser/components/about/AboutRedirector.cpp` and in `docshell/base/nsAboutRedirector.cpp`. We should disable several of them. Some don't work because the file is removed at compile time (e.g., `about:firefoxview`), others are still displayed (`about:pocket-*`), but non-functional. We could comment a few of them.