ui: fix "retrieve my username" typo (#12368)

Author: jfyuen

dojo/locale/en/LC_MESSAGES/django.po

@@ -3198,7 +3198,7 @@ msgid ""
 msgstr ""
 
 #: dojo/templates/dojo/forgot_username.html
-msgid "Retreive my username"
+msgid "Retrieve my username"
 msgstr ""
 
 #: dojo/templates/dojo/forgot_username_done.html

dojo/templates/login/forgot_username.html

@@ -9,7 +9,7 @@ <h3>{% translate 'Retrieve Username' %}</h3>
         {% include "dojo/form_fields.html" with form=form %}
         <div class="form-group">
         <div class="col-sm-offset-1 col-sm-1">
-            <button id="reset-password" class="btn btn-success">{% translate 'Retreive my username' %}</button>
+            <button id="reset-password" class="btn btn-success">{% translate 'Retrieve my username' %}</button>
         </div>
         </div>
     </fieldset>