Rename cod-btn into cod-button.

frontend/src/app/pages/signin/signin.component.html

@@ -34,6 +34,6 @@
     </div>
     <div class="actions reversed">
         <app-submit-button [requestPending]="false" [disabled]="false" i18n>Send</app-submit-button>
-        <a [routerLink]="['/login']" class="cod-btn secondary" matRipple i18n>I already have an account</a>
+        <a [routerLink]="['/login']" class="cod-button secondary" matRipple i18n>I already have an account</a>
     </div>
 </form>