Drop 'source_line' from data

[sarabveer]

This is an unmaintained field. Outside of Sri Guru Granth Sahib Ji, all the other compositions do not use this field in the intended manner or it is left null. Line numbers vary from source to source.

[bhajneet]

I understand this is an unmaintained/mis-used field currently. In the future, could this be used to locate lines programmatically in PDFs?

[sarabveer]

I understand this is an unmaintained/mis-used field currently. In the future, could this be used to locate lines programmatically in PDFs?

The line number (and even page number) varies from source to source. So at the current moment, the only PDF it could theoretically work with is Dr. Kulbir S. Thind's SGGS PDF (and that is assuming the source_line data is correct).