The PyQt resources system is gone in 6.2 and deprecated before that. This
should be the last usage of it.
Switches icons to be read with `utils.resources.read_file_binary()` in
`notification.py` (fallback desktop notification icon) and `app.py` (icon for
the desktop window).
importlib only loads resources under a package, so the icons are moved under
the `qutebrowser/` directory.
Closes: #6062
There is no html file being created ever, so trying to rebuild this target
would repeatedly build it from scratch, whether it existed or was up to date or
not. Plus it simply makes no sense to ask `make` for a .html file in order to
get a .1 file.
While we are at it, add a source dependency to rebuild the manpage on updates
to the asciidoc source, thus ensuring the newly corrected target name works as
intended.