fix(deps): bump alpine from 3.15.0 to 3.15.4

Bumps alpine from 3.15.0 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

@@ -6,7 +6,7 @@ COPY . .
 RUN go mod download && \
     CGO_ENABLED=0 go build -ldflags="-s -w" -o "wgcf"
 
-FROM alpine:3.15.0
+FROM alpine:3.15.4
 
 WORKDIR /