Upgrade ghcide

[vagifverdi]

ghcide has improvements both for space leaks and performance: https://mpickering.github.io/ide/posts/2020-06-12-performance-of-ghcide-020.html

When can these improvements be folded into haskell-language-server?

[wz1000]

See https://github.com/haskell/haskell-language-server/pull/160/files

[jneira]

Maybe we could close this one, it seems the requested improvements has been included with #160