feat(rust): Replace base64-url with base64

[Mr-Leshiy]

Description

Replace base64-url which is simply just a wrapper over base64 crate https://github.com/magiclen/base64-url/blob/7bcd29e6b1c21bc4b2592d40d9b493ab4ff3fad4/Cargo.toml#L16.
Simplify our dependency tree.

[github-actions]

✅ Test Report | ${\color{lightgreen}Pass: 302/302}$ | ${\color{red}Fail: 0/302}$ |

[stevenj]

This is not a necessary change. Not prioritized.
This change would then require a release and bumping other crates.
Not approved.