Make the banner subtitle white

The subtitle was pinned to #B5B5B5 inline. That read fine against the
flat violet header, but washed out once the banner became a photo behind
a lightened scrim.

Drop the inline override rather than hardcoding white: .jumbotron already
sets color: white, so the subtitle now inherits it along with the title
and stays consistent if that colour is ever changed.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_013CB1BSCz8YKpK4YyZiN81C

Author: jmxpearson

_includes/jumbotron.html

@@ -2,6 +2,8 @@
   <div class="container">
     <br>
     <h1>{{ page.title }}</h1>
-    <h5 style="color: #B5B5B5">{{ page.desc }}</h5>
+    <!-- No colour override: inherits white from .jumbotron. The old grey
+         (#B5B5B5) washed out once the flat violet header became a photo. -->
+    <h5>{{ page.desc }}</h5>
   </div>
 </div>