style(theme): keep REQUIRED label inline with schema title

When the parent summary became a flex row, the h3/strong holding the
title and the REQUIRED span fell back to block layout and wrapped.
Make the title element itself an inline-flex with a small gap so the
title and the badge stay on one line and align vertically.

Co-Authored-By: Claude Opus 4.7 <noreply@anthropic.com>

Author: sserrata

packages/docusaurus-theme-openapi-docs/src/theme/SchemaExpansion/_SchemaExpansion.scss

@@ -105,5 +105,9 @@
   > h3,
   > strong {
     margin-bottom: 0;
+    display: inline-flex;
+    align-items: center;
+    flex-wrap: wrap;
+    gap: 0.4rem;
   }
 }