Update GMRT coeffficients
This is in response to the comment by A. Botteon in the WSClean repository ( https://gitlab.com/aroffringa/wsclean/-/issues/40#note_1252697838 ): there are now band 2 (150-250 MHz) coefficients available, which were added, and bands 4 and 5 have updated coefficients. The new coefficients are here: