update string to be consistent

Author: Kimberley Cook

app/views/dashboard/show.html.haml

@@ -7,7 +7,7 @@
   .container.d-flex
     .col-md-5.offset-md-1.p-3.text
       %p.lead.mb-0= raw t('homepage.intro')
-      = link_to ('Join the codebar community'), new_member_path, class: 'btn btn-primary btn-lg mt-4'
+      = link_to ('Join our community'), new_member_path, class: 'btn btn-primary btn-lg mt-4'
 
 .py-4.py-lg-5.bg-light
   .container