fix: add vars for debian buster 10

[rafaelhdr]

I was having this issue with Debian 10

TASK [postgresql : PostgreSQL | Extensions | Make sure the postgis extensions are installed | Debian] ***
fatal: [172.20.1.10]: FAILED! => changed=false 
  msg: No package matching 'postgresql-12-postgis-scripts' is available

This PR was copy postgresql/vars/bionic.yml and edit the line 7:

-  - "postgresql-{{postgresql_version}}-postgis-scripts"
+  - "postgresql-{{postgresql_version}}-postgis-{{postgresql_ext_postgis_version}}-scripts"

[github-actions[bot]]

This pr has been marked 'stale' due to lack of recent activity. If there is no further activity, the issue will be closed in another 30 days. Thank you for your contribution!