[docker] Bump node from 21.6-alpine3.18 to 21.7-alpine3.18

Bumps node from 21.6-alpine3.18 to 21.7-alpine3.18.

---
updated-dependencies:
- dependency-name: node
  dependency-type: direct:production
...

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

Dockerfile.standalone

@@ -16,7 +16,7 @@ RUN --mount=type=cache,target=/go/pkg/mod \
     --mount=type=cache,target=/root/.cache/go-build \
     CGO_ENABLED=1 go build -mod vendor -ldflags "-s -w" -o authz ./cmd/
 
-FROM node:21.6-alpine3.18 as frontend-builder
+FROM node:21.7-alpine3.18 as frontend-builder
 
 ARG REACT_APP_API_BASE_URI=http://localhost:8080/v1
 ARG REACT_APP_DEMO_ENABLED=false