travis: ignore Laravel 6.0 failures for now

Too unstable it seems

Author: mfn

.travis.yml

@@ -53,8 +53,12 @@ matrix:
     - php: '7.4snapshot'
       env: LARAVEL='dev-master'
   allow_failures:
+    - php: '7.2'
+      env: LARAVEL='6.0.*'
     - php: '7.2'
       env: LARAVEL='dev-master'
+    - php: '7.3'
+      env: LARAVEL='6.0.*'
     - php: '7.3'
       env: LARAVEL='dev-master'
     - php: '7.4snapshot'