Remove deprecated methods of CryptoBackend#4671

florianduros merged 3 commits intoflorianduros/rip-out-legacy-crypto/remove-legacy-cryptomatrix-org/matrix-js-sdk:florianduros/rip-out-legacy-crypto/remove-legacy-cryptofrom

florianduros/rip-out-legacy-crypto/clean-up-cryptoBackendmatrix-org/matrix-js-sdk:florianduros/rip-out-legacy-crypto/clean-up-cryptoBackendCopy head branch name to clipboard