Bump cloud.google.com/go/security from 1.15.1 to 1.15.2 (sigstore#504)

Bumps [cloud.google.com/go/security](https://github.com/googleapis/google-cloud-go) from 1.15.1 to 1.15.2.
- [Release notes](https://github.com/googleapis/google-cloud-go/releases)
- [Changelog](https://github.com/googleapis/google-cloud-go/blob/main/CHANGES.md)
- [Commits](googleapis/google-cloud-go@kms/v1.15.1...kms/v1.15.2)

---
updated-dependencies:
- dependency-name: cloud.google.com/go/security
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <[email protected]>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

go.mod

@@ -3,7 +3,7 @@ module github.com/sigstore/timestamp-authority
 go 1.21
 
 require (
-	cloud.google.com/go/security v1.15.1
+	cloud.google.com/go/security v1.15.2
 	github.com/beevik/ntp v1.3.0
 	github.com/digitorus/pkcs7 v0.0.0-20230818184609-3a137a874352
 	github.com/digitorus/timestamp v0.0.0-20230902153158-687734543647

go.sum

@@ -41,8 +41,8 @@ cloud.google.com/go/pubsub v1.0.1/go.mod h1:R0Gpsv3s54REJCy4fxDixWD93lHJMoZTyQ2k
 cloud.google.com/go/pubsub v1.1.0/go.mod h1:EwwdRX2sKPjnvnqCa270oGRyludottCI76h+R3AArQw=
 cloud.google.com/go/pubsub v1.2.0/go.mod h1:jhfEVHT8odbXTkndysNHCcx0awwzvfOlguIAii9o8iA=
 cloud.google.com/go/pubsub v1.3.1/go.mod h1:i+ucay31+CNRpDW4Lu78I4xXG+O1r/MAHgjpRVR+TSU=
-cloud.google.com/go/security v1.15.1 h1:jR3itwycg/TgGA0uIgTItcVhA55hKWiNJxaNNpQJaZE=
-cloud.google.com/go/security v1.15.1/go.mod h1:MvTnnbsWnehoizHi09zoiZob0iCHVcL4AUBj76h9fXA=
+cloud.google.com/go/security v1.15.2 h1:VNpdJNfMeHSJZ+647QtzPrvZ6rWChBklLm/NY64RVW8=
+cloud.google.com/go/security v1.15.2/go.mod h1:2GVE/v1oixIRHDaClVbHuPcZwAqFM28mXuAKCfMgYIg=
 cloud.google.com/go/storage v1.0.0/go.mod h1:IhtSnM/ZTZV8YYJWCY8RULGVqBDmpoyjwiyrjsg+URw=
 cloud.google.com/go/storage v1.5.0/go.mod h1:tpKbwo567HUNpVclU5sGELwQWBDZ8gh0ZeosJ0Rtdos=
 cloud.google.com/go/storage v1.6.0/go.mod h1:N7U0C8pVQ/+NIKOBQyamJIeKQKkZ+mxpohlUTyfDhBk=