Bump alpine from 3.17 to 3.18 in /build (#635)

Bumps alpine from 3.17 to 3.18.

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

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

Author: dependabot[bot]

build/Dockerfile

@@ -14,7 +14,7 @@ COPY internal /go/src/github.com/nginxinc/nginx-kubernetes-gateway/internal
 COPY pkg /go/src/github.com/nginxinc/nginx-kubernetes-gateway/pkg
 RUN CGO_ENABLED=0 GOOS=linux go build -trimpath -a -ldflags "-s -w -X main.version=${VERSION} -X main.commit=${GIT_COMMIT} -X main.date=${DATE}" -o gateway .
 
-FROM alpine:3.17 as capabilizer
+FROM alpine:3.18 as capabilizer
 RUN apk add --no-cache libcap
 
 FROM capabilizer as local-capabilizer