internal/postgres: remove null bytes from license text
internal/postgres: remove null bytes from license text

pq and/or postgres doesn't like null (zero) bytes in TEXT columns.

At least one module (github.com/Velocidex/velociraptor) contains
license text with null bytes (the license actually appears to be corrupted).

Remove the null bytes so we can process the module. This can't change
the meaning of the license, since null bytes are non-printing.

Change-Id: I62b8929503776e0dcb2bc54d92d48f15ee653051
Reviewed-on: https://team-review.git.corp.google.com/c/golang/discovery/+/608337
Reviewed-by: Julie Qiu <e6cb64861edcc38971590ff27c111e0e672de045@google.com>

golang/pkgsite,golang/pkgsite,golang/pkgsite,golang/pkgsite