Prefer utf-8 over utf-32

Utf-8 support has been around for a while as an unstable feature but
utf-32 is fairly new. A bunch of LS (like rust-analyzer) added this in
a pinch, but it's pretty broken right now. The performance overhead is
not very large (still a lot better than utf-16). We can switch back
once the ecosystem has matured.

helix-lsp/src/client.rs

@@ -538,8 +538,8 @@ impl Client {
                 }),
                 general: Some(lsp::GeneralClientCapabilities {
                     position_encodings: Some(vec![
-                        PositionEncodingKind::UTF32,
                         PositionEncodingKind::UTF8,
+                        PositionEncodingKind::UTF32,
                         PositionEncodingKind::UTF16,
                     ]),
                     ..Default::default()