Check SGGS Author IDs

[Sarabveer Singh]

@sarabveer please track exploration of author ids in a new issue

— @bhajneet in #1791 (review)

The metadata for SGGS was taken from iGurbani. But as shown in #1763, it seems their data is problematic.

The Author/Writer IDs for SGGS should be either manually checked or re-imported from another source.

PR #1756 would address the 22 Vaars, but not the whole composition.