api!: Remove unused info_only option when loading a chatlist (#8171)

Remove unused info_only option from `get_chat_msgs_ex()`.

This option was meant to show an "audit log" of a group, i.e. only the
info messages. This feature was removed again from Desktop, but the
option still lingered around in Core.

This also adds a doc comment to the JsonRPC functions, because I
wanted to note somewhere that the parameter is deprecated, and I needed
some place to put this note.

deltachat-ffi/src/lib.rs

@@ -60,7 +60,6 @@ use self::string::*;
 // - finally, this behaviour matches the old core-c API and UIs already depend on it
 
 const DC_GCM_ADDDAYMARKER: u32 = 0x01;
-const DC_GCM_INFO_ONLY: u32 = 0x02;
 
 // dc_context_t
 
@@ -1338,17 +1337,13 @@ pub unsafe extern "C" fn dc_get_chat_msgs(
     }
     let ctx = &*context;
 
-    let info_only = (flags & DC_GCM_INFO_ONLY) != 0;
     let add_daymarker = (flags & DC_GCM_ADDDAYMARKER) != 0;
     block_on(async move {
         Box::into_raw(Box::new(
             chat::get_chat_msgs_ex(
                 ctx,
                 ChatId::new(chat_id),
-                MessageListOptions {
-                    info_only,
-                    add_daymarker,
-                },
+                MessageListOptions { add_daymarker },
             )
             .await
             .unwrap_or_log_default(ctx, "failed to get chat msgs")