Simplify the force_oauth related views

app/views/about/_login.html.haml

 = simple_form_for(new_user, url: user_session_path, namespace: 'login') do |f|
+  .fields-group
+    - if use_seamless_external_login?
+      = f.input :email, placeholder: t('simple_form.labels.defaults.username_or_email'), input_html: { 'aria-label' => t('simple_form.labels.defaults.username_or_email') }, hint: false
+    - else
+      = f.input :email, placeholder: t('simple_form.labels.defaults.email'), input_html: { 'aria-label' => t('simple_form.labels.defaults.email') }, hint: false
 
-  - if !Setting.force_oauth
-    .fields-group
-      - if use_seamless_external_login?
-        = f.input :email, placeholder: t('simple_form.labels.defaults.username_or_email'), input_html: { 'aria-label' => t('simple_form.labels.defaults.username_or_email') }, hint: false
-      - else
-        = f.input :email, placeholder: t('simple_form.labels.defaults.email'), input_html: { 'aria-label' => t('simple_form.labels.defaults.email') }, hint: false
+    = f.input :password, placeholder: t('simple_form.labels.defaults.password'), input_html: { 'aria-label' => t('simple_form.labels.defaults.password') }, hint: false
 
-      = f.input :password, placeholder: t('simple_form.labels.defaults.password'), input_html: { 'aria-label' => t('simple_form.labels.defaults.password') }, hint: false
-
-  - if Setting.force_oauth
-    .actions
-      = f.button :button, t('auth.login_sso'), type: :submit, class: 'button button-primary'
-  - else  
-    .actions
-      = f.button :button, t('auth.login'), type: :submit, class: 'button button-primary'
+  .actions
+    = f.button :button, t('auth.login'), type: :submit, class: 'button button-primary'
 
   %p.hint.subtle-hint= link_to t('auth.trouble_logging_in'), new_user_password_path

app/views/about/show.html.haml

@@ -13,7 +13,11 @@
 
   .landing__grid
     .landing__grid__column.landing__grid__column-registration
-      - if !Setting.force_oauth
+      - if Setting.force_oauth
+        .box-widget
+          .actions
+            = link_to t('auth.login_sso'), user_session_path
+      - else
         .box-widget
           = render 'registration'
 
@@ -46,8 +50,9 @@
               %small= t('about.apps_platforms')
 
     .landing__grid__column.landing__grid__column-login
-      .box-widget
-        = render 'login'
+      - if !Setting.force_oauth
+        .box-widget
+          = render 'login'
 
       .hero-widget
         .hero-widget__img