Update base64-serde requirement from 0.7 to 0.8 #595

Job	Run time
Clippy	45s
cargo-build (aarch64-linux-android, ubuntu-22.04)	3m 8s
format	12s
cargo-build (armv7-linux-androideabi, ubuntu-22.04)	3m 7s
cargo-test (ubuntu-22.04, default, stable)	6m 53s
cargo-build (i686-linux-android, ubuntu-22.04)	3m 1s
cargo-test (macos-12, default, stable)	8m 13s
cargo-test (windows-2019, default, stable)	9m 24s
cargo-build (x86_64-linux-android, ubuntu-22.04)	3m 5s
cargo-test (ubuntu-22.04, beta)	7m 17s
cargo-test (ubuntu-22.04, blocking)	7m 21s
cargo-build (x86_64-unknown-linux-musl, ubuntu-22.04)	3m 5s
cargo-test (ubuntu-22.04, blocking,beta)	7m 37s
cargo-build (aarch64-apple-ios, macos-12)	5m 4s
cargo-test (ubuntu-22.04, tls-rustls --no-default-features)	6m 58s
cargo-test (ubuntu-22.04, tls-vendored-openssl --no-default-features)	7m 33s
cargo-test (ubuntu-22.04, beta, default)	4m 5s
cargo-test (ubuntu-22.04, 1.75.0, default)	7m 2s
	1h 33m 50s

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