Declare required lsp-server dependency of rust-analyzer crate

My codebase already depended on lsp-server and introducing a dependency
on rust-analyzer failed at first because it assumes some functions that
were first present in lsp-server 0.3.2.

Without this change:

    error[E0599]: no method named `initialize_start` found for struct `lsp_server::Connection` in the current scope
      --> crates/rust-analyzer/./src/bin/main.rs:83:57
       |
    83 |     let (initialize_id, initialize_params) = connection.initialize_start()?;
       |                                                         ^^^^^^^^^^^^^^^^ method not found in `lsp_server::Connection`

    error[E0599]: no method named `initialize_finish` found for struct `lsp_server::Connection` in the current scope
      --> crates/rust-analyzer/./src/bin/main.rs:99:16
       |
    99 |     connection.initialize_finish(initialize_id, initialize_result)?;
       |                ^^^^^^^^^^^^^^^^^ method not found in `lsp_server::Connection`

0 files changed, 0 insertions, 0 deletions