Update var names

playbooks/mlapi_prod.yml

 - hosts: tag_Group_mlapi_prod
   vars_files:
-    - ["{{ secure_dir }}/vars/discern_prod_vars.yml"]
+    - ["{{ secure_dir }}/vars/mlapi_prod_vars.yml"]
     - ["{{ secure_dir }}/vars/users.yml"]
-    - ["{{ secure_dir }}/vars/discern_prod_users.yml"]
+    - ["{{ secure_dir }}/vars/mlapi_prod_users.yml"]
   roles:
     - common
     - discern

playbooks/mlapi_sandbox.yml

 - hosts:
     - tag_Group_mlapi_sandbox
   vars_files:
-    - ["{{ secure_dir }}/vars/discern_sandbox_vars.yml"]
+    - ["{{ secure_dir }}/vars/mlapi_sandbox_vars.yml"]
     - ["{{ secure_dir }}/vars/users.yml"]
-    - ["{{ secure_dir }}/vars/discern_sandbox_users.yml"]
+    - ["{{ secure_dir }}/vars/mlapi_sandbox_users.yml"]
   roles:
     - common
     - discern

playbooks/mlapi_stage.yml

 - hosts: tag_Group_mlapi_stage
   vars_files:
-    - ["{{ secure_dir }}/vars/discern_stage_vars.yml"]
+    - ["{{ secure_dir }}/vars/mlapi_stage_vars.yml"]
     - ["{{ secure_dir }}/vars/users.yml"]
-    - ["{{ secure_dir }}/vars/discern_stage_users.yml"]
+    - ["{{ secure_dir }}/vars/mlapi_stage_users.yml"]
   roles:
     - common
     - discern