Lisp: Remove brittle optimization in ambrevar/enhance-imenu-lisp.

It seems to break Emacs 27.1 with some packages.

.emacs.d/lisp/init-lisp.el

@@ -9,10 +9,9 @@
      'lisp-imenu-generic-expression
      (list (purecopy (concat (capitalize keyword) "s"))
            (purecopy (concat "^\\s-*("
-                             (eval-when-compile
-                               (regexp-opt
-                                (list (concat "define-" keyword))
-                                t))
+                             (regexp-opt
+                              (list (concat "define-" keyword))
+                              t)
                              "\\s-+\\(" lisp-mode-symbol-regexp "\\)"))
            2))))
 ;; Following defines are common, e.g. in Next.