Fix incorrect text-wrapping in the SubNav.SubHeading component on Safari (#1223)

Author: rezrah

.changeset/tasty-trees-complain.md

@@ -0,0 +1,5 @@
+---
+'@primer/react-brand': patch
+---
+
+Fixed incorrect text wrapping bug in `SubNav.SubHeading` on Safari browsers.

packages/react/src/SubNav/SubNav.features.stories.tsx

@@ -94,7 +94,7 @@ export const WithShadow: Story = {
 const SubHeadingTemplate = (args: SubNavProps) => (
   <SubNav {...args}>
     <SubNav.Heading href="#">AI</SubNav.Heading>
-    <SubNav.SubHeading href="#">Copilot</SubNav.SubHeading>
+    <SubNav.SubHeading href="#">GitHub Copilot</SubNav.SubHeading>
     <SubNav.Link href="#">For business</SubNav.Link>
     <SubNav.Link href="#" aria-current="page">
       Extensions

packages/react/src/SubNav/SubNav.module.css

@@ -489,6 +489,7 @@
 .SubNav__subHeading {
   display: block;
   position: relative;
+  white-space: nowrap;
 }
 
 .SubNav__subHeading[aria-current]:not([aria-current='false'])::after,