DeleteChangeUsingMultiGerrit1: Fix json change number

Before this change, the (change) number field used by that scenario was
solely automatic. Make that value either set from a composing scenario,
such as CreateChangeUsingMultiGerrit, or through the existing 'number'
test environment property; cf. [1]. DeleteChangeUsingMultiGerrit1 was
already able to be run standalone, so adjust that field accordingly.

[1] https://gerrit-documentation.storage.googleapis.com/Documentation/2.16.19/dev-e2e-tests.html#_environment_properties

Change-Id: Iace84c9eafe652e8c6160f508b57a481058f0162
diff --git a/src/test/resources/com/googlesource/gerrit/plugins/multisite/scenarios/DeleteChangeUsingMultiGerrit1.json b/src/test/resources/com/googlesource/gerrit/plugins/multisite/scenarios/DeleteChangeUsingMultiGerrit1.json
index 1190bbc..4b7f52e 100644
--- a/src/test/resources/com/googlesource/gerrit/plugins/multisite/scenarios/DeleteChangeUsingMultiGerrit1.json
+++ b/src/test/resources/com/googlesource/gerrit/plugins/multisite/scenarios/DeleteChangeUsingMultiGerrit1.json
@@ -1,6 +1,6 @@
 [
   {
     "url": "http://HOSTNAME:HTTP_PORT1/a/changes/",
-    "number": "_NUMBER"
+    "number": "NUMBER"
   }
 ]