Partially revert last change

There is no need to call eval on Emacs 26+, but tests fail in
earlier versions without it, so bring it back, but this time with
lexical-binding, at least.

* dev/examples-to-tests.el (example-to-should): Bring back eval.

dev/examples-to-tests.el

@@ -29,7 +29,8 @@
         ((eq sym '~>)
          `(should (approx-equal ,actual ,expected)))
         ((eq sym '!!>)
-         `(should-error ,actual :type ',expected))
+         ;; FIXME: Tests fail on Emacs 24-25 without `eval' for some reason.
+         `(should-error (eval ',actual lexical-binding) :type ',expected))
         ((error "Invalid test case: %S" `(,actual ,sym ,expected)))))
 
 (defmacro defexamples (cmd &rest examples)