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

[AlCutter]

#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