This addreses
https://github.com/rust-analyzer/rust-analyzer/issues/10464.
This patch picks up `lsp-types` 0.90.1, which serialises the
`SignatureInformation` and `ParameterInformation` with the right casing.
It also adds `activeSignature` field as part of the top-level signature
response. It keeps `activeParameter` at the top-level for backwards
compatibility.