Remove decompression support in proc-macro server

[Veykril]

rust-analyzer can probably also remove the support it has in rust-analyzer-proc-macro-server at

rust-analyzer/crates/proc-macro-srv/src/dylib/version.rs

Line 150 in 1aac2c6

Box::new(SnapDecoder::new(snappy_portion))

Originally posted by @bjorn3 in rust-lang/rust#132402 (comment)