Revert "commands: Read disableFastRender from flag even if it's not changed"

On second thought, removing this isn't worth it.

This reverts commit 78a4c2e32e.

commands/hugo.go

@@ -219,7 +219,6 @@ func initializeFlags(cmd *cobra.Command, cfg config.Provider) {
 
 	// Will set a value even if it is the default.
 	flagKeysForced := []string{
-		"disableFastRender",
 		"minify",
 	}