feat(editor): switch indent guide style to a thin line

As I'm no longer using whitespace-mode in prog-mode derived modes, the
cursor movement bug affecting highlight-indent-guides when
whitespace-mode is enabled is no longer an issue for me.

Further details about the highlight-indent-guides conflict with
whitespace-mode is available in this issue:
https://github.com/DarthFennec/highlight-indent-guides/issues/107

modules/editor/siren-highlight-indent-guides.el

@@ -14,7 +14,7 @@
   :custom
   (highlight-indent-guides-auto-enabled nil)
   (highlight-indent-guides-character ?\u2502)
-  (highlight-indent-guides-method 'column)
+  (highlight-indent-guides-method 'character)
   (highlight-indent-guides-responsive 'top))
 
 (provide 'siren-highlight-indent-guides)

modules/languages/siren-golang.el

@@ -38,7 +38,6 @@
       (auto-highlight-symbol-mode -1))
 
     (tree-sitter-mode +1)
-    (siren-display-indentation -1)
     (siren-folding)
     (subword-mode +1))