Problem:
`request()` and `notify()` are methods of the object returned by
`vim.lsp.rpc.start()`/`connect()`, but were rendered with module-level
helptags (`vim.lsp.rpc.request()`, `vim.lsp.rpc.notify()`) (erroneously
implying module functions that do not exist).
Solution:
Mark the wrappers `@private` and describe them on `vim.lsp.rpc.Client` instead.
6cbc5ea13d
