api: deprecate webxdc descr parameter (#6255)

this PR removes most usages of the `descr` parameter.

- to avoid noise in different branches etc. (as annoying on similar, at
a first glance simple changes), i left the external API stable

- also, the effort to do a database migration seems to be over the top,
so the column is left and set to empty strings on future updates - maybe
we can recycle the column at some point ;)

closes #6245

deltachat-jsonrpc/src/api.rs

@@ -1767,10 +1767,10 @@ impl CommandApi {
         account_id: u32,
         instance_msg_id: u32,
         update_str: String,
-        description: String,
+        _descr: String,
     ) -> Result<()> {
         let ctx = self.get_context(account_id).await?;
-        ctx.send_webxdc_status_update(MsgId::new(instance_msg_id), &update_str, &description)
+        ctx.send_webxdc_status_update(MsgId::new(instance_msg_id), &update_str)
             .await
     }