firmware: use correct symbol for git

Signed-off-by: Chris Fiege <chris@tinyhost.de>

flamingo/theme/templates/firmware.html

@@ -34,7 +34,7 @@
             <i class="fab fa-gitlab"></i> <a href="{{content.site}}" >Site Git Repository</a><br>
             {% endif %}
             {% if content.gluon is not none %}
-            <i class="fas fa-book"></i> <a href="{{content.gluon}}" >Gluon Git Repository</a><br>
+            <i class="fab fa-gitlab"></i> <a href="{{content.gluon}}" >Gluon Git Repository</a><br>
             {% endif %}
             {% if content.rtd is not none %}
             <i class="fas fa-book"></i> <a href="{{content.rtd}}" >Release Notes</a><br>