Revert "Add CPP to avoid warning with nightly flag disabled."

This reverts commit 30f4f85f91.

src/Text/Pandoc/App/CommandLineOptions.hs

@@ -56,11 +56,8 @@ import Text.Pandoc.Filter (Filter (..))
 import Text.Pandoc.Highlighting (highlightingStyles)
 import Text.Pandoc.Shared (ordNub, elemText, safeStrRead, defaultUserDataDir)
 import Text.Printf
-
-#ifdef NIGHTLY
 import Data.Time.Clock (UTCTime(utctDay), getCurrentTime)
 import Data.Time.Format (defaultTimeLocale, iso8601DateFormat, formatTime)
-#endif
 
 #ifdef EMBED_DATA_FILES
 import Text.Pandoc.Data (dataFiles)