Bump alpine from 3.15 to 3.18 in /12-alpine-3.15

Bumps alpine from 3.15 to 3.18.

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

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

12-alpine-3.15/Dockerfile

@@ -1,4 +1,4 @@
-FROM alpine:3.15
+FROM alpine:3.18
 
 LABEL org.opencontainers.image.source="https://github.com/cpp-linter/clang-tools-docker"
 LABEL org.opencontainers.image.description="The Clang Tools Docker image includes the clang-format and clang-tidy."