This appears to have been introduced ages ago in
be742a5877
but has since been removed.
As it stands, it is problematic if multiple instances of the
rust-analyzer LSP are launched during the same VS Code session because
VS Code complains about multiple LSP servers trying to register the
same command.
Most LSP servers workaround this by parameterizing the command by the
process id. For example, this is where `rls` does this:
ff0b9057c8/rls/src/server/mod.rs (L413-L421)
Though `apply_code_action` does not seems to be used, so it seems better
to delete it than to parameterize it.
