Bump golangci-lint and remove //nolint comments in experimental/batchmap/cmd/verify/verify.go

#2787 migrated Trillian to use `klog`. At the time, `golangci-lint`'s `staticcheck` did not know that `klog.Exit/Fatal` would not return and so threw false +ve lint checks during presubmit which were suppressed with `nolint` comments.

A fix has been sent which enlightens the lint checker, so once that fix has made it into a `golangci-lint` release (v1.48.0 did not contain it) we should bump the version used in our presubmits and remove the `//nolint` comments in [experimental/batchmap/cmd/verify/verify.go](https://github.com/google/trillian/pull/2787/files#diff-20e238926020c0e122f93aa474068b10dfcc62458920d5c5c1adfe7547a17e3bR102-R106)