gnu: flac: Upgrade to 1.3.0.

* gnu/packages/xiph.scm (flac): Update to version 1.3.0.
  Remove 'patches' field.
* gnu/packages/patches/flac-fix-memcmp-not-declared.patch: Remove.
* gnu-system.am (dist_patch_DATA): Adjust accordingly.

Signed-off-by: Jason Self <j@jxself.org>
Signed-off-by: Ludovic Courtès <ludo@gnu.org>