base64ct bump MSRV in non-breaking version

[AurelienFT]

Hello,

Thanks for the work on maintaining these crates. We just saw that you updated base64ct to bump the MSRV to 1.85 in your 1.7.0 version.

However I think that bumping the MRSV in a non-breaking version is not well managed by cargo and brake a lot of projects that see their crates automatically upgraded (by semver managed by cargo) and prevent their project of compiling.

What do you think of that ? I think it should be better to change MSRV in a major version. If you agree we can help make a new non-breaking to rollback this change and create a breaking version. As you want :)

[tarcieri]

Dup of #1684