Fix: fix title of 422 page (#3979)

## Because
- The error code in the title accidentally says `500` instead of `422`


## This PR
- Changes it to 422


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  - `Fix` - bug fixes
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app/views/errors/unprocessable_entity.html.erb

@@ -1,4 +1,4 @@
-<%= title('Unprocessable entity (500)') %>
+<%= title('Unprocessable entity (422)') %>
 
 <p class="text-base text-gold-600">422</p>
 <h1 class="mt-4 text-5xl text-slate-900 font-bold">Unprocessable entity</h1>