BoringSSL is now Apache 2.0, like OpenSSL (github.com)

OpenSSL 3.0 relicensed to Apache 2.0, but BoringSSL was a fork of OpenSSL from before the relicense, so it still had the old OpenSSL license. With this change, BoringSSL is now Apache 2.0 as well, which helps everyone wanting to use it in GPLed code.