ref(option): change this flag to use automator instead of admin (#54123)

Was recommended by @fpacifici to use this flag instead of the admin
modifiable flag.

src/sentry/options/defaults.py

@@ -1424,7 +1424,11 @@ register(
 )
 
 # The flag activates whether to send group attributes messages to kafka
-register("issues.group_attributes.send_kafka", default=False, flags=FLAG_MODIFIABLE_BOOL)
+register(
+    "issues.group_attributes.send_kafka",
+    default=False,
+    flags=FLAG_MODIFIABLE_BOOL | FLAG_AUTOMATOR_MODIFIABLE,
+)
 
 # Enables statistical detectors for a project
 register(