[Fix #1176] Remove smart-mode-line

As mentioned in the issue - it's causing problems on Emacs 26.1.

core/prelude-packages.el

@@ -80,7 +80,6 @@
     magit
     move-text
     operate-on-number
-    smart-mode-line
     smartparens
     smartrep
     undo-tree

core/prelude-ui.el

@@ -74,12 +74,6 @@
 (when prelude-theme
   (load-theme prelude-theme t))
 
-(require 'smart-mode-line)
-(setq sml/no-confirm-load-theme t)
-;; delegate theming to the currently active theme
-(setq sml/theme nil)
-(add-hook 'after-init-hook #'sml/setup)
-
 ;; show the cursor when moving after big movements in the window
 (require 'beacon)
 (beacon-mode +1)