Bump rustls for client_auth_cert method

[stagnation]

It was added in the 0.21.5 point release. Errors took the following form:

$ ~/task/buck2 cargo build
error[E0599]: no method named `with_client_auth_cert` found for struct `ConfigBuilder` in the current scope
   --> app/buck2_http/src/tls.rs:126:10
    |
123 | /     ClientConfig::builder()
124 | |         .with_safe_defaults()
125 | |         .with_root_certificates(system_roots)
126 | |         .with_client_auth_cert(cert, key)
    | |         -^^^^^^^^^^^^^^^^^^^^^ help: there is a method with a similar name: `with_no_client_auth`
    | |_________|

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