Update oc new-app example to latest imagestream tag name

[dmc5179]

Update oc new-app example to latest imagestream tag name. The current command in the README.md is:

oc new-app httpd:24~https://github.com/sclorg/httpd-ex.git

On OpenShift 4.9 this results in the following message:

oc new-app httpd:24~https://github.com/sclorg/httpd-ex.git
error: multiple images or templates matched "httpd:24"

The argument "httpd:24" could apply to the following container images, OpenShift image streams, or templates:

* Image stream "httpd" (tag "2.4-el7") in project "openshift"
  Use --image-stream="openshift/httpd:2.4-el7" to specify this image or template

* Image stream "httpd" (tag "2.4-el8") in project "openshift"
  Use --image-stream="openshift/httpd:2.4-el8" to specify this image or template

* Image stream "httpd" (tag "latest") in project "openshift"
  Use --image-stream="openshift/httpd:latest" to specify this image or template

Changing the command to the latest imagestream tag name resolves this issue:

oc new-app openshift/httpd:2.4-el8~https://github.com/sclorg/httpd-ex.git

[dmc5179]

#126