build(deps): bump alpine from 3.13 to 3.15.0

Bumps alpine from 3.13 to 3.15.0.

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

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

Dockerfile

@@ -12,7 +12,7 @@ RUN go mod download
 # Build the docker-gen executable
 RUN GOOS=linux CGO_ENABLED=0 go build -ldflags "-X main.buildVersion=${VERSION}" -o docker-gen ./cmd/docker-gen
 
-FROM alpine:3.13
+FROM alpine:3.15.0
 
 LABEL maintainer="Nicolas Duchon <[email protected]> (@buchdag)"