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.

test/Feature/ConcurrentSpec.hs

@@ -5,7 +5,6 @@
 module Feature.ConcurrentSpec where
 
 import Control.Concurrent.Async (mapConcurrently)
-import Control.Monad            (void)
 import Network.Wai              (Application)
 
 import Control.Monad.Base

test/Feature/InsertSpec.hs

@@ -2,7 +2,6 @@ module Feature.InsertSpec where
 
 import qualified Data.Aeson as JSON
 
-import Control.Monad          (replicateM_, void)
 import Data.List              (lookup)
 import Data.Maybe             (fromJust)
 import Network.Wai            (Application)

test/Feature/UnicodeSpec.hs

@@ -1,7 +1,6 @@
 module Feature.UnicodeSpec where
 
-import Control.Monad (void)
-import Network.Wai   (Application)
+import Network.Wai (Application)
 
 import Test.Hspec
 import Test.Hspec.Wai

test/SpecHelper.hs

@@ -7,7 +7,6 @@ import qualified Data.Map.Strict        as M
 import qualified Data.Set               as S
 import qualified System.IO.Error        as E
 
-import Control.Monad        (void)
 import Data.Aeson           (Value (..), decode, encode)
 import Data.CaseInsensitive (CI (..))
 import Data.List            (lookup)