Add PG14 to CI configs

Author: hanefi

.travis.yml

@@ -13,6 +13,7 @@ matrix:
     - env: PGVERSION=11
     - env: PGVERSION=12
     - env: PGVERSION=13
+    - env: PGVERSION=14
 before_install:
   - bash test_data_provider
   - git clone -b v0.7.13 --depth 1 https://github.com/citusdata/tools.git