Fix glossary section header font size to absolute 13px

Prevents headers from rendering too small on mobile portrait orientation.

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via [Happy](https://happy.engineering)

Co-Authored-By: Claude <noreply@anthropic.com>
Co-Authored-By: Happy <yesreply@happy.engineering>

Author: 3 people

docs/projects/grcengineering-cheat-sheet/index.html

@@ -383,7 +383,7 @@
 .glossary-section:last-child { margin-bottom: 0; }
 .glossary-section-title {
   font-family: var(--font-mono);
-  font-size: 0.7rem;
+  font-size: 13px;
   font-weight: 700;
   letter-spacing: 3px;
   text-transform: uppercase;