cicd: excluded PG 9.6 from MASTER build

Author: cuprumtan

.github/workflows/mamonsu-tests-master.yml

@@ -18,7 +18,7 @@ jobs:
       matrix:
         docker_os: ['ubuntu:20.04', 'centos:7', 'centos:8']
         zabbix_version: ['4.0', '5.0', '5.4']
-        pg_version: ['9.6', '10', '11', '12', '13', '14']
+        pg_version: ['10', '11', '12', '13', '14']
 
     steps:
       - name: Checkout Mamonsu repo