Bump alpine from 3.21.3 to 3.22.2 in /web

Bumps alpine from 3.21.3 to 3.22.2.

---
updated-dependencies:
- dependency-name: alpine
  dependency-version: 3.22.2
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

Author: dependabot[bot]

web/Dockerfile

@@ -1,5 +1,5 @@
 # syntax = docker/dockerfile:1.3
-FROM alpine:3.21.3
+FROM alpine:3.22.2
 
 # Add requirements file.
 COPY requirements.txt /tmp/

web/Dockerfile.dev

@@ -1,5 +1,5 @@
 # syntax = docker/dockerfile:1.3
-FROM alpine:3.21.3
+FROM alpine:3.22.2
 
 ARG POSTORIUS_REF
 ARG HYPERKITTY_REF