Fix: use emacs 28 compat completion fns in test

Author: joshbax189

test/capf-tests.el

@@ -46,8 +46,9 @@ E.g. should complete \"Array.\" to all properties."
     (sit-for 1)
     (insert "Array.")
     (completion-at-point)
-    (minibuffer-next-completion)
-    (minibuffer-choose-completion)
+    (with-minibuffer-completions-window
+      (next-completion 1)
+      (choose-completion))
     (should (looking-back "Array.__proto__"))))
 
 (ert-deftest js-comint/test-capf-complete-long-line ()
@@ -59,8 +60,9 @@ E.g. 'if (true) { console.'"
     (sit-for 1)
     (insert "if (true) { console.")
     (completion-at-point)
-    (minibuffer-next-completion)
-    (minibuffer-choose-completion)
+    (with-minibuffer-completions-window
+      (next-completion 1)
+      (choose-completion))
     (should (looking-back "console.__proto__"))))
 
 (ert-deftest-async js-comint/test-capf-no-props (done)