improvement(scylla-bench): bump version to v0.1.21

[vponomaryov]

It uses the most recent gocql version - v1.14.1

Testing

• https://jenkins.scylladb.com/view/staging/job/scylla-staging/job/valerii/job/vp-longevity-large-partition-8h-test/9

PR pre-checks (self review)

• I added the relevant backport labels
• I didn't leave commented-out/debugging code

Reminders

• Add New configuration option and document them (in sdcm/sct_config.py)
• Add unit tests to cover my changes (under unit-test/ folder)
• Update the Readme/doc folder relevant to this change (if needed)

[fruch]

@vponomaryov

do we have any reference of a job running with it ?

meanwhile I've enable the integration tests, to a see it in action

[vponomaryov]

@vponomaryov

do we have any reference of a job running with it ?

meanwhile I've enable the integration tests, to a see it in action

Passed here: https://jenkins.scylladb.com/view/staging/job/scylla-staging/job/valerii/job/vp-longevity-large-partition-8h-test/9

[fruch]

LGTM