Fix Prev/Next navigation buttons when viewing article (#15439)

Earlier both the on the left and right buttons had the text `Next>>` now
the left one will have the text `<< Prev`

fixes: https://github.com/kubernetes/website/issues/15438

Signed-off-by: Harsh Vardhan <harsh.vardhan@mayadata.io>

layouts/blog/pager.html

@@ -1,7 +1,7 @@
 <div class="PageNavigation">
 	 {{ if .PrevInSection }}
     <div class="pagerButton left">
-        <h4><a class=" button" href="{{ .PrevInSection.RelPermalink }}"> {{ T "layouts_blog_pager_next" }} </a></h4>
+        <h4><a class=" button" href="{{ .PrevInSection.RelPermalink }}"> {{ T "layouts_blog_pager_prev" }} </a></h4>
     </div>
     {{ end }}
     {{ if .NextInSection }}
@@ -9,4 +9,4 @@
         <h4><a class=" button" href="{{ .NextInSection.RelPermalink }}"> {{ T "layouts_blog_pager_next" }} </a></h4>
     </div>
     {{ end }}
- </div>
+ </div>