Update pipeline to test the latest TAS

Author: tas-operability-bot

ci/pipelines/pas-pipeline-tasks/values.yml

@@ -6,3 +6,4 @@ tas_versions:
     - {'version_slug': '4-0', 'pool_name': 'tas_four' , 'pivnet_ert_windows': '^4\.0\.\d+((-alpha|-beta|-rc)\.\d+)?(\+LTS-T)?$' }
     - {'version_slug': '5-0', 'pool_name': 'tas-5_0' , 'pivnet_ert_windows': '^5\.0\.\d+((-alpha|-beta|-rc)\.\d+)?(\+LTS-T)?$' }
     - {'version_slug': '6-0', 'pool_name': 'tas-6_0' , 'pivnet_ert_windows': '^6\.0\.\d+((-alpha|-beta|-rc)\.\d+)?(\+LTS-T)?$' }
+    - {'version_slug': 'tas-7', 'pool_name': 'tas_7_prerelease' , 'pivnet_ert_windows': '^tas\.7\.\d+((-alpha|-beta|-rc)\.\d+)?(\+LTS-T)?$' }