Update MaxAstroTides from 56 to 77

In syspars.f90 there is a list with all the indices of the constituents available in COHERENS. 77 in total.

The number of tidal constituents available to compute harmonic part of elevation/transport is MaxConstituents = 77. So we can use of all them.

The number of tidal constituents available to compute astronomical tidal force MaxAstroTides = 56. So if we use constituent with an index greater than 56 we get an error like this

Invalid value for element 10 of integer array index_astro: 63

Must be between: 1 and 56

Invalid value for element 13 of integer array index_astro: 64

Must be between: 1 and 56

Invalid value for element 15 of integer array index_astro: 62

Must be between: 1 and 56

A total of 3 errors occurred in check_mod_params

Error type 7 : Invalid initial values for model parameters or arrays

The MaxAstroTides must be reset to 77.