perf(org): optimize org-roam node listings

org-roam-get-keyword performs some file IO to read file keywords from
all nodes. This can be slow with long node lists. With
org-roam/org-roam#1963, file title is baked into the schema, so we don't
need to do this work anymore.

Ref: org-roam/org-roam#1963
Fix: #6382

modules/lang/org/autoload/contrib-roam2.el

@@ -8,7 +8,7 @@
 If there's no file-level title in the file, return empty string."
   (or (if (= (org-roam-node-level node) 0)
           (org-roam-node-title node)
-        (org-roam-get-keyword "TITLE" (org-roam-node-file node)))
+        (org-roam-node-file-title node))
       ""))
 
 ;;;###autoload (autoload 'org-roam-node-doom-hierarchy "lang/org/autoload/contrib-roam2" nil t)