This patch updates clamav to the latest LTS version.
Per the release notes [1], a future update of clamav to 0.105+ will take some effort:

1. 0.105+ needs Rust 1.57+ to build.
2. The build should switch from tarball to git to avoid vendored crates.
3. 0.105+ works with llvm 8-12 (no more llvm 3.7).

I suggest we keep clamav on the LTS version until we update Rust.

PS: As you can see from the email address, I am migrating from Tutanota to Disroot.

[1] https://blog.clamav.net/2022/05/clamav-01050-01043-01036-released.html#more