These imports are not strictly needed and can be the source of
dependency cycles if certain GN/GNI files get imported in some
ways, so we better remove them and eliminate that friction.
Additionally, this change implies that we need to explicitly add
an import for brave/components/decentralized_dns/buildflags in
brave/browser/profiles/BUILD.gn now, since that file needs the
definitions for decentralized_dns that were previously being
imported via brave/components/tor/buildflags/buildflags.gni:
brave/browser/profiles/BUILD.gn
└─> brave/components/tor/buildflags/buildflags.gni
└─> build/config/features.gni
└─> build/config/chrome_build.gni
└─> brave/build/config/brave_build.gni
└─> brave/net/sources.gni
└─> brave/components/decentralized_dns/buildflags/buildflags.gni
... but now that build/config/features.gni is no longer being
imported from brave/components/tor/buildflags/buildflags.gni, we
need to explicitly add the import to brave/browser/profiles/BUILD.gn
or we'll get a new gn check failure.
Resolves https://github.com/brave/brave-browser/issues/15171
Mario Sanchez Prada
ec8635f9f9