Drop support for GHC <8.4

The newly added Text.XML.Soap module doesn't support it anyway

Author: mniip

dom-parser.cabal

@@ -44,13 +44,12 @@ library
                      , TypeFamilies
                      , TypeOperators
                      , UndecidableInstances
-  build-depends:       base >= 4.7 && < 5
+  build-depends:       base >= 4.11 && < 5
                      , case-insensitive
                      , containers
                      , lens
                      , mtl
                      , scientific
-                     , semigroups
                      , text
                      , transformers
                      , xml-conduit

src/Text/XML/DOM/Parser/Combinators.hs

@@ -22,7 +22,6 @@ import Control.Monad.Reader
 import Data.Foldable as F
 import Data.List as L
 import Data.List.NonEmpty (NonEmpty(..))
-import Data.Monoid
 import Data.Text as T
 import Data.Traversable
 import Text.XML

src/Text/XML/DOM/Parser/Types.hs

@@ -36,7 +36,6 @@ import Control.Lens
 import Control.Monad.Except
 import Control.Monad.Reader
 import Data.CaseInsensitive as CI
-import Data.Semigroup
 import Data.String
 import Data.Text as T
 import GHC.Generics (Generic)