Upgrade from php7.4 to php8.2.

[funilrys]

As php7.4 has reach its end of life 8 months ago, I thought it was time to upgrade.

I tested the change with a compose that looks like the one below. I also tested against some of my private sites and everything worked without any noticeable issue.

WARNING: The data are not persistent with the following compose.

---
version: '2.1'
services:
  gravadmin:
    build:
      context: .
      dockerfile: Dockerfile.gravadmin
      args:
        GRAV_VERSION: 1.7.42.3
    container_name: gravadmin
    restart: unless-stopped
    environment:
      - DUID=1001
      - DGID=1001
      #- GRAV_MULTISITE=subdirectory # optional
      - ROBOTS_DISALLOW=false # optional
    ports:
      - 8080:80
  gravcore:
    build:
      context: .
      dockerfile: Dockerfile.gravcore
      args:
        GRAV_VERSION: 1.7.42.3
    container_name: gravcore
    restart: unless-stopped
    environment:
      - DUID=1001
      - DGID=1001
      #- GRAV_MULTISITE=subdirectory # optional
      - ROBOTS_DISALLOW=false # optional
    ports:
      - 8888:80

CF: https://endoflife.date/php

@dsavell The contribution guidelines page is empty.

---

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[dsavell]

Heya,

Thank you for your contribution, I have finally been able to get round to getting this image updated.

Please see #65 for these changes I have consolidated.