source/index.rst: update Mastodon RelMe link

Author: Saijin-Naib

source/index.rst

@@ -1,6 +1,6 @@
 .. raw:: html
 
-   <a rel="me" style="visibility:hidden" aria-hidden="true"  href="https://fosstodon.org/@OpenDroneMap"></a>
+   <a rel="me" style="visibility:hidden" aria-hidden="true"  href="https://fedi.opendronemap.org/@OpenDroneMap"></a>
 
 .. figure:: https://www.opendronemap.org/wp-content/uploads/2018/07/odm-logo.svg
    :alt: OpenDroneMap Logo