fix(super-tab): tab should respect manual selection

[minusfive]

When using the super-tab preset and the completion.list.selection option is set to "manual", the custom <Tab> keymap doesn't respect it and still selects and accepts the first option.

Simply ensuring cmp.accept() is triggered when this option is set (instead of cmp.select_and_accept()) works because cmp.accept() internally checks whether a completion item is selected, and if it isn't it exits without executing anything.