build(deps): bump alpine from 3.15.3 to 3.15.4

Bumps alpine from 3.15.3 to 3.15.4.

---
updated-dependencies:
- dependency-name: alpine
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>

Dockerfile

@@ -22,13 +22,13 @@ COPY . .
 
 RUN make release-binary
 
-FROM alpine:3.15.3 AS stager
+FROM alpine:3.15.4 AS stager
 
 RUN mkdir -p /var/dex
 RUN mkdir -p /etc/dex
 COPY config.docker.yaml /etc/dex/
 
-FROM alpine:3.15.3 AS gomplate
+FROM alpine:3.15.4 AS gomplate
 
 ARG TARGETOS
 ARG TARGETARCH