alias `{r,i}_hsc` to `{r,i}2_hsc`

[monodera]

Currently, most users use {r,i}2_hsc filters as HSC r and i filters, respectively. In fact, many users use {r,i}_hsc as flux columns in their target lists, so our requirement seems a bit confusing for them. This requirement is most important for flux standards, not for objects. Therefore, we could assume {r,i}_hsc as {r,i}2_hsc filters.