re-add previously removed "7.3" IS tag (#444)

we need to maintain it for the lifetime of this image.

Author: zmiklank

imagestreams/imagestreams.yaml

@@ -33,6 +33,10 @@
 
       - name: UBI 9
         app_versions: ["8.0", "8.1"]
+    custom_tags:
+      - name: "7.3"
+        distro: UBI 7
+        app_version: "7.3"
 
   - filename: php-rhel-aarch64.json
     latest: "8.0-ubi8"

imagestreams/php-rhel.json

@@ -104,6 +104,25 @@
           "type": "Local"
         }
       },
+      {
+        "name": "7.3",
+        "annotations": {
+          "openshift.io/display-name": "PHP 7.3 (UBI 7)",
+          "openshift.io/provider-display-name": "Red Hat, Inc.",
+          "description": "Build and run PHP 7.3 applications on UBI 7. For more information about using this builder image, including OpenShift considerations, see https://github.com/sclorg/s2i-php-container/blob/master/7.3/README.md.",
+          "iconClass": "icon-php",
+          "tags": "builder,php",
+          "version": "7.3",
+          "sampleRepo": "https://github.com/sclorg/cakephp-ex.git"
+        },
+        "from": {
+          "kind": "DockerImage",
+          "name": "registry.redhat.io/ubi7/php-73:latest"
+        },
+        "referencePolicy": {
+          "type": "Local"
+        }
+      },
       {
         "name": "latest",
         "annotations": {