build(deps): bump alpine from 3.14.3 to 3.15.0

Bumps alpine from 3.14.3 to 3.15.0.

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

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

Dockerfile

@@ -1,4 +1,4 @@
-FROM docker.io/alpine:3.14.3
+FROM docker.io/alpine:3.15.0
 
 ARG DUMB_INIT_PACKAGE_VERSION=1.2.5-r1
 ARG NETCAT_PACKAGE_VERSION=1.130-r2