pack/internal/packtest: remove redundant parens in type conv
pack/internal/packtest: remove redundant parens in type conv

Simplified (int)(v) to int(v).

Change-Id: I0fd6f3ed57158101212ce7f7d3af0e9be936c094
Reviewed-on: https://upspin-review.googlesource.com/19060
Reviewed-by: Rob Pike <4dc7c9ec434ed06502767136789763ec11d2c4b7@golang.org>

upspin/upspin,upspin/upspin