Update to protolude 0.3.0

The good part is that protolude 0.3.0 builds with GHC 8.10.

The bad part is that this change is a bit painful:
- the default `toS` has changed to no longer convert to and from ByteString
- similarly, `show` no longer outputs ByteString

The changes here are pretty much minimal to keep things compiling; I didn't
see a nice way to work with the new ConvertText class, even though `toUtf8`
seems like it might help if used besides `toS` at just the right spots.

main/Main.hs

@@ -33,7 +33,8 @@ import PostgREST.OpenAPI     (isMalformedProxyUri)
 import PostgREST.Types       (ConnectionStatus (..), DbStructure,
                               PgVersion (..), Schema,
                               minimumPgVersion)
-import Protolude             hiding (hPutStrLn, head, replace)
+import Protolude             hiding (hPutStrLn, head, replace, toS)
+import Protolude.Conv        (toS)
 
 
 #ifndef mingw32_HOST_OS