Update getrandom-sgx to v2.3

We're currently trying to update our substrate dependencies to v4.0.0-dev (see issue https://github.com/integritee-network/worker/issues/346). But substrate now depends on hashbrown 0.11.0 which itself depends on getrandom 2.3 (same as in issue #326). We're currently in the development phase, so having our own getrandom fork and keeping it up to date all the time is not yet necessary from a security perspective. A simple patch to your [getrandom-sgx](https://github.com/mesalock-linux/getrandom-sgx) crate would be enough.

Would it be possible to update [getrandom-sgx](https://github.com/mesalock-linux/getrandom-sgx) to v2.3 so we can apply the patch?

Thanks alot for your help so far!

Start by reading the dependency context in issues #346 and #326, then inspect how this repository references the getrandom-sgx crate. Check the linked getrandom-sgx project for the v2.3 update path and verify that the resulting patch can be applied to the current Substrate dependency set; done means the SDK can use getrandom 2.3 without its dependency conflict.

Written by the indexing model from the issue text.