Fix php-docker example (for new docker versions)

[ci skip]

doc/ci/examples/php.md

@@ -40,7 +40,7 @@ repository with the following content:
 #!/bin/bash
 
 # We need to install dependencies only for Docker
-[[ ! -e /.dockerinit ]] && exit 0
+[[ ! -e /.dockerenv ]] && [[ ! -e /.dockerinit ]] && exit 0
 
 set -xe