ci: Remove Brewfile

a4cbf3e4 removed macOS from the CI.
We couldn't get it to build and no community member stepped up.
So let's remove this file now as well.

Brewfile

@@ -1,22 +0,0 @@
-brew 'autoconf'
-brew 'autoconf-archive'
-brew 'automake'
-brew 'check'
-brew 'cmocka'
-brew 'curl'
-brew 'expat'
-brew 'glib'
-brew 'gnutls'
-brew 'gpgme'
-brew 'gtk+'
-brew 'libffi'
-brew 'libotr'
-brew 'libsignal-protocol-c'
-brew 'libstrophe'
-brew 'libtool'
-brew 'ncurses'
-brew 'openssl'
-brew 'ossp-uuid'
-brew 'pkg-config'
-brew 'readline'
-brew 'sqlite'