Disallow wildcard dependencies with cargo-deny

[TimJentzsch]

We don't want to allow wildcard dependencies, as they might allow dependency upgrades with breaking changes.
However, cargo-deny currently treats all git dependencies as wildcards, even when the commit hash is fixed.

We need to wait for EmbarkStudios/cargo-deny#488 to switch this back.
Then we can change the corresponding entry in deny.toml.

[TimJentzsch]

This is no longer blocked, see EmbarkStudios/cargo-deny#487

We need to use the allow-wildcard-paths option in the bans section.

[TimJentzsch]

Seems like the issue is not fully resolved yet.

[alice-i-cecile]

We're no longer using any git dependencies, so this is unblocked.