Bump sigstore/cosign/cosign from v3.0.3 to v3.0.4 in /builds (#2020)

Bumps sigstore/cosign/cosign from v3.0.3 to v3.0.4.

---
updated-dependencies:
- dependency-name: sigstore/cosign/cosign
  dependency-version: v3.0.4
  dependency-type: direct:production
...

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

Author: dependabot[bot]

builds/Dockerfile

@@ -1,5 +1,5 @@
 ARG STACK_VERSION="24"
-FROM ghcr.io/sigstore/cosign/cosign:v3.0.3@sha256:774391ac9f0c137ee419ce56522df5fd3b1f52be90c5b77e97f7c053bdd67a67 AS cosign
+FROM ghcr.io/sigstore/cosign/cosign:v3.0.4@sha256:0b015a3557a64a751712da8a6395534160018eaaa2d969882a85a336de9adb70 AS cosign
 FROM heroku/heroku:${STACK_VERSION}-build
 
 ARG STACK_VERSION