[Combobox] Update openOnFocus example to work even with empty input

The existing openOnFocus example mounts/unmounts the popover based on
the results array state, which returns null if the input term is an
empty string. This is confusing in the context of the openOnFocus prop
because the popover doesn't show on focus if the input is empty.

packages/combobox/examples/open-on-focus.example.js

@@ -6,15 +6,13 @@ import {
   ComboboxOption,
   ComboboxPopover,
 } from "@reach/combobox";
-import { useCityMatch } from "./utils";
 import "@reach/combobox/styles.css";
 
 let name = "Open on focus";
 
 function Example() {
-  let [term, setTerm] = React.useState("D");
+  let [term, setTerm] = React.useState("");
   let [selection, setSelection] = React.useState("");
-  let results = useCityMatch(term);
   let inputRef = React.useRef(null);
 
   function handleChange(event) {
@@ -37,21 +35,15 @@ function Example() {
           style={inputStyle}
           ref={inputRef}
         />
-        {results && (
-          <ComboboxPopover style={popupStyle}>
-            <p>
-              <button>Hi</button>
-            </p>
-            <ComboboxList>
-              {results.slice(0, 10).map((result, index) => (
-                <ComboboxOption
-                  key={index}
-                  value={`${result.city}, ${result.state}`}
-                />
-              ))}
-            </ComboboxList>
-          </ComboboxPopover>
-        )}
+        <ComboboxPopover>
+          <ComboboxList>
+            <ComboboxOption value="Apple" />
+            <ComboboxOption value="Banana" />
+            <ComboboxOption value="Orange" />
+            <ComboboxOption value="Pineapple" />
+            <ComboboxOption value="Kiwi" />
+          </ComboboxList>
+        </ComboboxPopover>
       </Combobox>
     </div>
   );