ENH: Fix the Documentation PR title identification

Fix the `Documentation`PR title identification: avoid having two entries
for the `area:Documentation` label, and use the newly created
`type:Documentation` for the PR title regex.

Author: jhlegarreta

.github/labeler.yml

@@ -5,7 +5,7 @@ type:Compiler:
 type:Bug:
   title: "^BUG:.*"
 
-area:Documentation:
+type:Documentation:
   title: "^DOC:.*"
 
 type:Enhancement: