flac: foreign_metadata: fix -Walloc-size

[thesamesam]

GCC 14 introduces a new -Walloc-size included in -Wextra which gives:

src/flac/foreign_metadata.c:803:33: warning: allocation of insufficient size ‘1’ for type ‘foreign_metadata_t’ with size ‘64’ [-Walloc-size]

The calloc prototype is:

void *calloc(size_t nmemb, size_t size);

So, just swap the number of members and size arguments to match the prototype, as we're initialising 1 struct of size sizeof(foreign_metadata_t). GCC then sees we're not doing anything wrong.

[thesamesam]

Thanks!