Add `delete` binding for clearing auto-suggestion (#13990)

Closes  #13987 assuming that we have a consensus.

IPython/terminal/shortcuts/__init__.py

@@ -208,6 +208,11 b' AUTO_SUGGEST_BINDINGS = ['
         "has_suggestion & default_buffer_focused & emacs_insert_mode",
     ),
     Binding(
+        auto_suggest.discard,
+        ["delete"],
+        "has_suggestion & default_buffer_focused & emacs_insert_mode",
+    ),
+    Binding(
         auto_suggest.swap_autosuggestion_up,
         ["up"],
         "navigable_suggestions"