doc: Add RHEL7 image info/job link into FAQ

Signed-off-by: Stewart X Addison <sxa@redhat.com>

FAQ.md

@@ -85,6 +85,7 @@ have at the moment:
 | Dockerfile | Image | Platforms  | Where is this built? | In use?
 |---|---|---|---|---|
 | [Centos7](./ansible/docker/Dockerfile.CentOS7) | [`adoptopenjdk/centos7_build_image`](https://hub.docker.com/r/adoptopenjdk/centos7_build_image) | linux on amd64, arm64, ppc64le | [Jenkins](https://ci.adoptium.net/job/centos7_docker_image_updater/) | Yes
+| [RHEL7](./ansible/docker/Dockerfile.RHEL7) | n/a - restricted | s390x | [Jenkins](https://ci.adoptium.net/job/rhel7_docker_image_updater/) | Yes
 | [Centos6](./ansible/docker/Dockerfile.CentOS6) | [`adoptopenjdk/centos6_build_image`](https://hub.docker.com/r/adoptopenjdk/centos6_build_image)| linux/amd64 | [GH Actions](.github/workflows/build.yml) | Yes
 | [Alpine3](./ansible/docker/Dockerfile.Alpine3) | [`adoptopenjdk/alpine3_build_image`](https://hub.docker.com/r/adoptopenjdk/alpine3_build_image) | linux/x64 & linux/arm64 | [Jenkins](https://ci.adoptium.net/job/centos7_docker_image_updater/) | Yes
 | [Ubuntu 20.04 (riscv64 only)](./ansible/docker/Dockerfile.Ubuntu2004-riscv64) | [`adoptopenjdk/ubuntu2004_build_image:linux-riscv64`](https://hub.docker.com/r/adoptopenjdk/ubuntu2004_build_image) | linux/riscv64 | [Jenkins](https://ci.adoptium.net/job/centos7_docker_image_updater/) | Yes