feat(editor): remove hideshowvis package

The folding indicators in the fringe haven't been working when clicked
for some time now. And they also take precedence over other things
displayed in the fringe like git status.

modules/editor/siren-folding.el

@@ -17,8 +17,7 @@
   (defun siren-folding (&optional arg)
     "Activate or deactivate code folding.
 Optional ARG is passed directly to mode toggle function."
-    (hs-minor-mode (or arg t))
-    (if window-system (hideshowvis-minor-mode (or arg t))))
+    (hs-minor-mode (or arg t)))
 
   (defun siren-folding-toggle (column)
     "Toggle hiding/showing blocks via hs-mode.
@@ -40,8 +39,5 @@ Borrowed from: http://www.emacswiki.org/emacs/HideShow"
          (unless selective-display
            (1+ (current-column)))))))
 
-(use-package hideshowvis
-  :defer t)
-
 (provide 'siren-folding)
 ;;; siren-folding.el ends here