Change to solid to match formatting of other icons

Signed-off-by: Tracy Kuhrt <tracy.a.kuhrt@accenture.com>

mkdocs.yml

@@ -88,7 +88,7 @@ extra:
       link: https://discord.gg/openwalletfoundation
     - icon: fontawesome/solid/envelope
       link: https://lists.openwallet.foundation
-    - icon: fontawesome/regular/calendar-days
+    - icon: fontawesome/solid/calendar-days
       link: https://zoom-lfx.platform.linuxfoundation.org/meetings/openwalletfoundation
     - icon: fontawesome/solid/globe
       link: https://openwallet.foundation