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.

src/PostgREST/Statements.hs

@@ -29,7 +29,8 @@ import           PostgREST.Private.Common
 import           PostgREST.Private.QueryFragment
 import           PostgREST.Types
 import           Protolude                       hiding (cast,
-                                                  replace)
+                                                  replace, toS)
+import           Protolude.Conv                  (toS)
 import           Text.InterpolatedString.Perl6   (qc)
 
 {-| The generic query result format used by API responses. The location header