[CI:DOCS]use nginx in podman tutorial

the podman tutorial refers to an old httpd image based on Fedora 29.  It
is x86_64 only so Apple Silicon Macs and RPI's cannot follow the
tutorial.  Switch to nginx

Fixes: #20916

[NO NEW TESTS NEEDED]

Signed-off-by: Brent Baude <bbaude@redhat.com>

docs/tutorials/podman_tutorial.md

@@ -21,10 +21,7 @@ For installing or building Podman, see the [installation instructions](https://p
 This sample container will run a very basic httpd server (named basic_httpd) that serves only its index
 page.
 ```console
-podman run --name basic_httpd -dt -p 8080:8080/tcp -e HTTPD_VAR_RUN=/run/httpd -e HTTPD_MAIN_CONF_D_PATH=/etc/httpd/conf.d \
-                  -e HTTPD_MAIN_CONF_PATH=/etc/httpd/conf \
-                  -e HTTPD_CONTAINER_SCRIPTS_PATH=/usr/share/container-scripts/httpd/ \
-                  registry.fedoraproject.org/f29/httpd /usr/bin/run-httpd
+podman run --name basic_httpd -dt -p 8080:80/tcp docker.io/nginx
 ```
 Because the container is being run in detached mode, represented by the *-d* in the `podman run` command, Podman
 will print the container ID after it has run. Note that we use port forwarding to be able to

docs/tutorials/podman_tutorial_cn.md

@@ -23,10 +23,7 @@ Podman是由libpod库提供一个实用的程序，可以被用于创建和管
 这个示例容器会运行一个简单的只有主页的 httpd 服务器。
 
 ```console
-podman run -dt -p 8080:8080/tcp -e HTTPD_VAR_RUN=/run/httpd -e HTTPD_MAIN_CONF_D_PATH=/etc/httpd/conf.d \
-                  -e HTTPD_MAIN_CONF_PATH=/etc/httpd/conf \
-                  -e HTTPD_CONTAINER_SCRIPTS_PATH=/usr/share/container-scripts/httpd/ \
-                  registry.fedoraproject.org/f29/httpd /usr/bin/run-httpd
+podman run --name basic_httpd -dt -p 8080:80/tcp docker.io/nginx
 ```
 
 因为命令中的 *-d* 参数表明容器以 "detached" 模式运行，所以 Podman 会在容器运行后打印容器的 ID。