Make shift-delete also delete current autosuggestion

This is a bit more convenient than using "history delete".

CHANGELOG.rst

@@ -138,6 +138,7 @@ New or improved bindings
   For example, ``commandline -f yank -f yank-pop`` inserts the last-but-one entry from the kill ring.
 - When the cursor is on a command that resolves to an executable script, :kbd:`alt-o` will now open that script in your editor (:issue:`10266`).
 - During up-arrow history search, :kbd:`shift-delete` will delete the current search item and move to the next older item. Previously this was only supported in the history pager.
+  Same for autosuggestions.
 - Some improvements to the :kbd:`alt-e` binding which edits the commandline in an external editor:
   - The editor's cursor position is copied back to fish. This is currently supported for Vim and Kakoune.
   - Cursor position synchronization is only supported for a set of known editors. This has been extended by also resolving aliases. For example use ``complete --wraps my-vim vim`` to synchronize cursors when `EDITOR=my-vim`.

src/reader.rs

@@ -2579,11 +2579,20 @@ impl ReaderData {
             }
             rl::HistoryPagerDelete => {
                 // Also applies to ordinary history search.
-                if !self.history_search.is_at_end() {
-                    self.history.remove(self.history_search.current_result());
+                let is_history_search = !self.history_search.is_at_end();
+                if is_history_search || !self.autosuggestion.is_empty() {
+                    self.history.remove(if is_history_search {
+                        self.history_search.current_result()
+                    } else {
+                        &self.autosuggestion.text
+                    });
                     self.history.save();
-                    self.history_search.handle_deletion();
-                    self.update_command_line_from_history_search();
+                    if is_history_search {
+                        self.history_search.handle_deletion();
+                        self.update_command_line_from_history_search();
+                    } else {
+                        self.autosuggestion.clear();
+                    }
                     self.inputter.function_set_status(true);
                     return;
                 }