Button separators should follow every button in the responsive form

[oleq]

Follow-up of #7704.

📝 Provide detailed reproduction steps (if any)

1. http://fake.ckeditor.com:8125/ckeditor5/tests/manual/all-features.html
2. Create a link.

✔️ Expected result

The separator should only be displayed after the save button.

❌ Actual result

This especially becomes a problem when the form gets some padding:

📃 Other details

• OS: master

---

If you'd like to see this fixed sooner, add a 👍 reaction to this post.

[oleq]

Changes required:

diff --git a/packages/ckeditor5-theme-lark/theme/ckeditor5-ui/components/responsive-form/responsiveform.css b/packages/ckeditor5-theme-lark/theme/ckeditor5-ui/components/responsive-form/responsiveform.css
index 6c93c08802..c4250b0ee9 100644
--- a/packages/ckeditor5-theme-lark/theme/ckeditor5-ui/components/responsive-form/responsiveform.css
+++ b/packages/ckeditor5-theme-lark/theme/ckeditor5-ui/components/responsive-form/responsiveform.css
@@ -6,7 +6,7 @@
 @import "@ckeditor/ckeditor5-ui/theme/mixins/_rwd.css";
 @import "@ckeditor/ckeditor5-ui/theme/mixins/_dir.css";

-.ck-vertical-form .ck-button::after {
+.ck-vertical-form > .ck-button:nth-last-child(2)::after {
          border-right: 1px solid var(--ck-color-base-border);
 }

@@ -48,10 +48,11 @@
                            }
                   }

-                  /* 'button' selector must be used because those styles shouldn't be added to other elements, like 'a'. Example in LinkActionsView. */
-                  & button.ck-button {
+                  /* Styles for two last buttons in the form (save&cancel, edit&unlink, etc.). */
+                  & > .ck-button:nth-last-child(1),
+                  & > .ck-button:nth-last-child(2) {
                            padding: var(--ck-spacing-standard);
                            border-radius: 0;
                            border: 0;