[libshumate] Make ShumateDataSource abstract

[Marcus Lundblad <mlundblad src gnome org>]

commit 31908ca5132b94d895f6ac94f95d350bd5fbb47c
Author: James Westman <james jwestman net>
Date:   Fri Jul 29 11:12:36 2022 -0500

    Make ShumateDataSource abstract

 shumate/shumate-data-source.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)
---
diff --git a/shumate/shumate-data-source.c b/shumate/shumate-data-source.c
index f37c51d..e720545 100644
--- a/shumate/shumate-data-source.c
+++ b/shumate/shumate-data-source.c
@@ -23,7 +23,7 @@
  * The base class used to retrieve tiles as [struct@GLib.Bytes].
  */
 
-G_DEFINE_TYPE (ShumateDataSource, shumate_data_source, G_TYPE_OBJECT)
+G_DEFINE_ABSTRACT_TYPE (ShumateDataSource, shumate_data_source, G_TYPE_OBJECT)
 
 
 enum