librustls: remove duplicative out param null check

In `rustls_client_connection_new` we're using the pattern of
constructing a `&mut *mut` out reference from a `*mut *mut` pointer
input using the `try_mut_from_ptr_ptr!` macro, which checks that the
param isn't `NULL`. This means an earlier explicit check isn't needed
and can be removed for clarity.

Author: cpu

librustls/src/client.rs

@@ -762,9 +762,6 @@ impl rustls_client_config {
         conn_out: *mut *mut rustls_connection,
     ) -> rustls_result {
         ffi_panic_boundary! {
-            if conn_out.is_null() {
-                return rustls_result::NullParameter;
-            }
             let server_name = unsafe {
                 if server_name.is_null() {
                     return rustls_result::NullParameter;