Transition delay improvement - Listing 15.10

[pradoh97]

Instead of applying transition-delay to the nav labels always, just apply it on hover. Changing the selector from:
.nav-links > li:nth-child(n) .nav-links__label
to
.nav-links:hover > li:nth-child(n) .nav-links__label
helps preventing the delay when using tab to navigate (different timings in appearances are noticeable) also it removes the delay while transitioning from the hover to the normal state.