docs: replace legacy line‑dot‑left‑horizontal icons with unified dot icon across docs

apps/docs/content/(01-linear-structures)/hash-table/49-group-anagrams.mdx

@@ -1,7 +1,7 @@
 ---
 title: '49. Group Anagrams'
 description: Given an array of strings strs, group the anagrams together. You can return the answer in any order
-icon: line-dot-left-horizontal
+icon: dot
 sidebar:
   label: 'Group Anagrams'
   badge: 'Medium'