Allow php 7.3 to failed while waiting for it in vendor

Jeremiah VALERIE · Jeremiah VALERIE · commit cf9ed60df7a1 · 2018-12-15T18:19:30.000+01:00
diff --git a/.travis.yml b/.travis.yml
@@ -20,6 +20,7 @@ branches:
 matrix:
   allow_failures:
     - php: nightly
+    - php: 7.3
 
 cache:
   directories:
