Server: remove rustix via clap bump (#1110)

Same boat for `svix-server` as with `svix-bridge` in #1109

Bumping clap removes the sole runtime dependency on `rustix`, but it
still exists in the dep tree impacting only compile-time code paths.

```
$ cargo tree -p [email protected] -i
rustix v0.38.4
└── tempfile v3.7.0
    ├── figment v0.10.10
    │   └── svix-server v1.13.0 (/home/onelson/Projects/svix-webhooks/server/svix-server)
    ├── prost-build v0.9.0
    │   └── tonic-build v0.6.2
    │       [build-dependencies]
    │       └── opentelemetry-otlp v0.10.0
    │           └── svix-server v1.13.0 (/home/onelson/Projects/svix-webhooks/server/svix-server)
    └── sqlx-macros-core v0.7.1
        └── sqlx-macros v0.7.1 (proc-macro)
            └── sqlx v0.7.1
                ├── sea-orm v0.12.2
                │   └── svix-server v1.13.0 (/home/onelson/Projects/svix-webhooks/server/svix-server)
                ├── sea-query-binder v0.5.0
                │   └── sea-orm v0.12.2 (*)
                └── svix-server v1.13.0 (/home/onelson/Projects/svix-webhooks/server/svix-server)
```

Updating sea-orm, and otel-related deps will help get the affected
`rustix` version out of our tree entirely, but it's a larger lift.

Refs: https://github.com/svix/svix-webhooks/security/dependabot/74