Fix 'invalid insertion' panic when following

Wait for the necessary buffer operations to arrive before attempting to
set selections and scroll top.

crates/language/src/buffer.rs

@@ -1313,10 +1313,10 @@ impl Buffer {
         self.text.wait_for_edits(edit_ids)
     }
 
-    pub fn wait_for_anchors<'a>(
+    pub fn wait_for_anchors(
         &mut self,
-        anchors: impl IntoIterator<Item = &'a Anchor>,
-    ) -> impl Future<Output = Result<()>> {
+        anchors: impl IntoIterator<Item = Anchor>,
+    ) -> impl 'static + Future<Output = Result<()>> {
         self.text.wait_for_anchors(anchors)
     }