Bump schnorrkel to 0.11.5

[haikoschol]

This change bumps the schnorrkel dependency to 0.11.5 in order to avoid indirectly depending on the potentially vulnerable crate curve25519-dalek-ng.

The motivation for doing this is to get rid of curve25519-dalek-ng in Polkadot SDK and verifiable is the last direct dependency which pulls it in:

polkadot-sdk$ cargo tree --invert curve25519-dalek-ng
curve25519-dalek-ng v4.1.1
└── schnorrkel v0.10.2
    └── verifiable v0.1.0

Related issue: paritytech/polkadot-sdk#4852

[eskimor]

@Zebedeusz can we get this merged and a release cut?

[Zebedeusz]

@eskimor Let me do a few checks and I'll let you know. Today or tomorrow at the latest.

[Zebedeusz]

I had to make some changes to make it work - rand with getrandom was causing issues.

[gui1117]

I had to make some changes to make it work - rand with getrandom was causing issues.

what was causing issue? it is compiling fine to me without the rand change.