What was the significance of the Proviso omitted by the Sixtieth Amendment Act, 1988, s.2 (w.e.f. 20-12-1988)?
The context provided is a constitutional amendment related to taxation and financial matters. However, there is no mention of any specific proviso in the context. Therefore, it's not possible to provide the significance of the Proviso omitted by the Sixtieth Amendment Act, 1988, s.2 (w.e.f. 20-12-1988) based on this information alone.