Update Rust crate base64 to 0.22

[renovate]

This PR contains the following updates:

Package	Type	Update	Change
base64	dependencies	minor	0.21 → 0.22

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Release Notes

marshallpierce/rust-base64 (base64)

v0.22.1

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• Correct the symbols used for the predefined alphabet::BIN_HEX.

v0.22.0

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• DecodeSliceError::OutputSliceTooSmall is now conservative rather than precise. That is, the error will only occur if the decoded output cannot fit, meaning that Engine::decode_slice can now be used with exactly-sized output slices. As part of this, Engine::internal_decode now returns DecodeSliceError instead of DecodeError, but that is not expected to affect any external callers.
• DecodeError::InvalidLength now refers specifically to the number of valid symbols being invalid (i.e. len % 4 == 1), rather than just the number of input bytes. This avoids confusing scenarios when based on interpretation you could make a case for either InvalidLength or InvalidByte being appropriate.
• Decoding is somewhat faster (5-10%)

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