[calls] about: Update authors

[Evangelos Ribeiro Tzaras <devrtz src gnome org>]

commit 1f0ad8cf7c9a92834d69708eb887205ea5d40b6c
Author: Evangelos Ribeiro Tzaras <evangelos tzaras puri sm>
Date:   Thu Jul 15 10:57:11 2021 +0200

    about: Update authors

 src/calls-main-window.c | 2 ++
 1 file changed, 2 insertions(+)
---
diff --git a/src/calls-main-window.c b/src/calls-main-window.c
index 8fff4e79..a7cb8366 100644
--- a/src/calls-main-window.c
+++ b/src/calls-main-window.c
@@ -92,6 +92,8 @@ about_action (GSimpleAction *action,
     "Adrien Plazas <kekun plazas laposte net>",
     "Bob Ham <rah settrans net>",
     "Guido Günther <agx sigxcpu org>",
+    "Julian Sparber <julian sparber net>",
+    "Evangelos Ribeiro Tzaras <devrtz fortysixandtwo eu>",
     NULL
   };