fix(messages): inputlist() offers the mouse when it cannot be used (#41280)

Problem:
`inputlist()` advertises "click with the mouse" purely because it
implements click selection, so under the default `'mouse'` of "nvi" it
offers a click that command-line mode never receives.

Solution:
Only offer the mouse when `'mouse'` covers command-line mode, the same
condition `:help inputlist()` already documents.

test/functional/ui/cmdline_spec.lua

@@ -1007,7 +1007,7 @@ describe('cmdline redraw', function()
       {3:                                                                           }|
       foo                                                                        |
       bar                                                                        |
-      Type number and <Enter> or click with the mouse (q or empty cancels): ^     |
+      Type number and <Enter> (q or empty cancels): ^                             |
     ]])
     command('redraw')
     screen:expect_unchanged()