update free tier to 10-digit MGRS on redgridtactical.com

Author: RedGridTactical

docs/mgrs.html

@@ -250,7 +250,7 @@ <h2 class="section-title text-center mb-4">Pricing</h2>
           <div class="amount">$0</div>
           <div class="period">forever</div>
           <ul>
-            <li>Live MGRS display (4-digit / 1km)</li>
+            <li>Live 10-digit MGRS (1m precision)</li>
             <li>3 tactical tools</li>
             <li>3 report templates</li>
             <li>1 waypoint</li>