Provide better error message for abuse contact phone number

Make it clear that all the user need to do to rectify is to provide a phone number

-------------
Created by MOE: https://github.com/google/moe
MOE_MIGRATED_REVID=153191178

java/google/registry/ui/server/registrar/RegistrarSettingsAction.java

@@ -286,7 +286,8 @@ public class RegistrarSettingsAction implements Runnable, JsonActionRunner.JsonA
           && !any(newContactsByType.get(type), HAS_PHONE)) {
         throw new ContactRequirementException(
             String.format(
-                "At least one %s contact must have a phone number", type.getDisplayName()));
+                "Please provide a phone number for at least one %s contact",
+                type.getDisplayName()));
       }
     }
   }

javatests/google/registry/ui/server/registrar/ContactSettingsTest.java

@@ -125,8 +125,8 @@ public class ContactSettingsTest extends RegistrarSettingsActionTestCase {
         "op", "update",
         "args", reqJson));
     assertThat(response).containsEntry("status", "ERROR");
-    assertThat(response).containsEntry("message", "At least one "
-        + RegistrarContact.Type.TECH.getDisplayName() + " contact must have a phone number");
+    assertThat(response).containsEntry("message", "Please provide a phone number for at least one "
+        + RegistrarContact.Type.TECH.getDisplayName() + " contact");
   }
 
   @Test
@@ -149,7 +149,7 @@ public class ContactSettingsTest extends RegistrarSettingsActionTestCase {
         "op", "update",
         "args", reqJson));
     assertThat(response).containsEntry("status", "ERROR");
-    assertThat(response).containsEntry("message", "At least one "
-        + RegistrarContact.Type.ABUSE.getDisplayName() + " contact must have a phone number");
+    assertThat(response).containsEntry("message", "Please provide a phone number for at least one "
+        + RegistrarContact.Type.ABUSE.getDisplayName() + " contact");
   }
 }