fix: disable NuGet audit in nethermind Dockerfile (#1036)

NuGet's vulnerability database was updated after Nethermind 1.36.2's
release to flag Microsoft.AspNetCore.DataProtection 10.0.1 as critically
vulnerable (GHSA-9mv3-2cwr-p262). Since Nethermind treats warnings as
errors, dotnet restore fails with NU1904 on every PR.

Disable NuGet audit at build time with -p:NuGetAudit=false to unblock
CI. The fix is merged upstream (NethermindEth/nethermind#11331) and
included in 1.37.0 (pre-release). Once a stable Nethermind release
ships with the patched dependency, we bump NETHERMIND_TAG and remove
this flag.