test: remove dead PR3068 workaround branch (#6109)

`WORKAROUND_ENABLING_ROLLBACK_OF_PR3068` compared the 5-element
`sys.version_info` tuple to `(3, 9)`, so it was always False. The guarded
branch never ran. Remove the constant and keep only the branch that runs.

Assisted-by: ClaudeCode:claude-opus-5
1 file changed