Reduce the cache times for capability checks

[stevegrunwell]

Currently, capability checks against the API (e.g. "is this domain permitted to embed media on the front-end via shortcode?") are cached for 12 hours. That's not normally a huge deal except when a subscriber wants to enable a domain capability but then either has to flush the cache or wait up to 12 hours to get access to the capability.

Since the capability check is only run when attempting to render the shortcode, a much shorter cache time (1min or so) should be used — long enough to keep the API happy but short enough that the shortcode would start working almost instantly.