Use haskell-lsp-0.20

[jneira]

• Bumping up in build config files
• A minor change due to the new type definition of NormalizedUri
• Closes use haskell-lsp-0.20 #1643 and fixes Lint error: hGetContents: invalid argument (invalid byte sequence) (Win10 + Atom) #1560 (this time for real)

[jneira]

Maybe caching in azure is a little bit strict: it is throwed away if you even add a space in the stack.yaml.
It makes forcing cache invalidation less necessary but bumping out one dependency invalidates it.