refactor(header): removed border from last toolbar when using collapsible large title (#22891)

resolves #22777

BREAKING CHANGE: The last toolbar in the header with a collapsible large title no longer has a border.

BREAKING.md

@@ -13,6 +13,7 @@ This is a comprehensive list of the breaking changes introduced in the major ver
 ## Version 6.x
 
 - [Components](#components)
+  * [Header](#header)
   * [Toast](#toast)
 - [Config](#config)
   * [Transition Shadow](#transition-shadow)
@@ -21,6 +22,18 @@ This is a comprehensive list of the breaking changes introduced in the major ver
 
 ### Components
 
+#### Header
+
+When using a collapsible large title, the last toolbar in the header with `collapse="condense"` no longer has a border. This does not affect the toolbar when the large title is collapsed.
+
+To get the old style back, add the following CSS to your global stylesheet:
+
+```css
+ion-header.header-collapse-condense ion-toolbar:last-of-type {
+  --border-width: 0 0 0.55px;
+}
+```
+
 #### Toast
 
 The `--white-space` CSS variable now defaults to `normal` instead of `pre-wrap`.

core/src/components/header/header.ios.scss

@@ -60,6 +60,10 @@
   z-index: 0;
 }
 
+.header-collapse-condense ion-toolbar:last-of-type {
+  --border-width: 0px;
+}
+
 .header-collapse-condense ion-toolbar ion-searchbar {
   height: 48px;