Bump alpine from 3.19.1 to 3.20.0 in /web (#696)

Bumps alpine from 3.19.1 to 3.20.0.

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

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

web/Dockerfile

@@ -1,5 +1,5 @@
 # syntax = docker/dockerfile:1.3
-FROM alpine:3.19.1
+FROM alpine:3.20.0
 
 # Add requirements file.
 COPY requirements.txt /tmp/

web/Dockerfile.dev

@@ -1,5 +1,5 @@
 # syntax = docker/dockerfile:1.3
-FROM alpine:3.19.1
+FROM alpine:3.20.0
 
 ARG POSTORIUS_REF
 ARG HYPERKITTY_REF