Only test upgrade from latest release

Author: swiatekm

testing/integration/testdata/.upgrade-test-agent-versions.yml

@@ -5,10 +5,4 @@
 # upgrade integration tests.
 
 testVersions:
-  - 9.2.2-SNAPSHOT
   - 9.2.1
-  - 9.1.8-SNAPSHOT
-  - 9.1.7
-  - 8.19.8-SNAPSHOT
-  - 8.19.7
-  - 7.17.30-SNAPSHOT