Add btn-default class to all default buttons (#6521)

plugins/discourse-local-dates/assets/javascripts/discourse/templates/components/discourse-local-dates-create-form.hbs

@@ -112,7 +112,7 @@
 
 <div class="modal-footer discourse-local-dates-create-modal-footer">
   {{#if validDate}}
-    {{d-button class="btn"
+    {{d-button class="btn btn-default"
       action="save"
       label="discourse_local_dates.create.form.insert"}}
   {{/if}}
@@ -122,7 +122,7 @@
   </a>
 
   {{d-button
-    class="advanced-mode-btn"
+    class="btn-default advanced-mode-btn"
     action=(action "advancedMode")
     icon="cog"
     label=toggleModeBtnLabel}}