hugo: use i18n string for 'caution' alerts

While we don't currently use the caution alert anywhere yet, we should
still be consistent in using i18n strings for these (not `title
.AlertType`).

Signed-off-by: David Karlsson <35727626+dvdksn@users.noreply.github.com>

i18n/en.yaml

@@ -17,6 +17,7 @@ important: Important
 note: Note
 tip: Tip
 warning: Warning
+caution: Caution
 
 ## openapi strings:
 

layouts/_default/_markup/render-blockquote.html

@@ -28,7 +28,7 @@
       <span class="icon-svg pb-1">{{ $i := index $icons .AlertType }}
         {{ partialCached "icon.html" $i $i }}
       </span>
-      <strong>{{ or (i18n .AlertType) (title .AlertType) }}</strong>
+      <strong>{{ i18n .AlertType }}</strong>
     </p>
     {{ .Text | safeHTML }}
   </blockquote>