Upgrading Alpine version to 3.18 in the PHP 8.1 image

[yhakbar]

Description

Upgrading Alpine version to 3.18 in the PHP 8.1 image.

Related issues

Please forgive me for not opening an issue first, I don't know if that's a requirement for the procedure of requesting an update in this repo.

Purpose

The update here is being introduced to allow for the AWS CLI v2 to be installed in the image without having to compile from source:

$ docker run --rm --entrypoint ash php:8.1-fpm-alpine3.16 -c 'apk add --no-cache aws-cli && aws --version'
...
aws-cli/1.22.81 Python/3.10.12 Linux/5.15.49-linuxkit-pr botocore/1.21.49

$ docker run --rm --entrypoint ash php:8.1-fpm-alpine3.18 -c 'apk add --no-cache aws-cli && aws --version'
...
aws-cli/2.13.5 Python/3.11.4 Linux/5.15.49-linuxkit-pr source/aarch64.alpine.3 prompt/off

[timkelty]

Nope, a PR is just fine!

Thanks so much!!!!