multimedia/libass: Update to 0.17.4

Remove leftover USES=autoreconf from when we were fetching from GitHub.
We've been using pre-rolled releases since 0ffcdbd9 (2020-26-09) and
we don't patch the autotools files.

Elevate CPE_VENDOR and USE_LDCONFIG to USES block (portclippy).

Sort OPTIONS_DEFINE/OPTIONS_DEFAULT (portclippy).

Align whitespace within blocks for readability.

https://github.com/libass/libass/releases/tag/0.17.4