Remove unused imports (with newer protolude)

The changes here are from fixing stack build with LTS 15.8 (GHC 8.8.3)
to be warning-free. Most if not all come from the newer protolude
version, which adds some things like `unwords`.

So to make sure that we don't get unused import warnings with newer
stackage, this both raises the protolude lower bound and removes
these imports.

src/PostgREST/Statements.hs

@@ -22,8 +22,6 @@ import           Data.Aeson                      as JSON
 import qualified Data.Aeson.Lens                 as L
 import qualified Data.ByteString.Char8           as BS
 import           Data.Maybe
-import           Data.Text                       (unwords)
-import           Data.Text.Encoding              (encodeUtf8)
 import qualified Hasql.Decoders                  as HD
 import qualified Hasql.Encoders                  as HE
 import qualified Hasql.Statement                 as H