Replace RLS with rust-analyzer in ch00

[zica87]

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Because Rust Language Server is deprecated now.

[BlacRyu]

I just started learning Rust and reading the rust book. I had already heard about rust-analyzer when following guides for setting up my IDE, and the Rust Language Server sounded very similar so I was curious how the two were related. I discovered that they basically do the same thing, and that RLS was officially deprecated over a year ago in favor of rust-analyzer. It would be nice if this PR could go through to help avoid confusion, especially as it is right at the front of the book which is almost certainly read by the most people.