go/scanner: align line and column limit with the compiler's limit

go/scanner: align line and column limit with the compiler's limit

The compiler disallows line and column numbers > (1<<30)
(cmd/compiler/internal/syntax.PosMax).

Set the go/scanner limit to the same rather than off by one.

For #59180

Change-Id: Ibf9e0e6826d6f6230b0d492543b7e906298a0524
Reviewed-on: https://go-review.googlesource.com/c/go/+/482595
TryBot-Result: Gopher Robot <gobot@golang.org>
Reviewed-by: Matthew Dempsky <mdempsky@google.com>
Run-TryBot: Damien Neil <dneil@google.com>