fix: Correct K6_PROMETHEUS_RW_TLS_MINIMUM_VERSION env var

[fatmcgav]

What?

The env var implemented in grafana/k6#5537 is K6_PROMETHEUS_RW_TLS_MINIMUM_VERSION, whereas the docs suggest K6_PROMETHEUS_RW_TLS_MIN_VERSION.

Updating docs to reflect implmeneted env var.

Checklist

• I have used a meaningful title for the PR.
• I have described the changes I've made in the "What?" section above.
• I have performed a self-review of my changes.
• I have run the npm start command locally and verified that the changes look good.

• I have made my changes in the docs/sources/k6/next folder of the documentation.
• I have reflected my changes in the docs/sources/k6/v{most_recent_release} folder of the documentation.
• I have reflected my changes in the relevant folders of the two previous k6 versions of the documentation (if still applicable to previous versions).

• I have made my changes in the docs/sources/k6/next folder of the documentation.

Related PR(s)/Issue(s)

grafana/k6#5537

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[heitortsergent]

@fatmcgav thanks for opening the PR! You're right, it looks the variable name is wrong.

Would you mind updating the file in the two previous versions as well? If not, that's ok, I can just merge your PR and open a separate one to do that. 😇

[fatmcgav]

@heitortsergent Yeh, should be able to later today or tomorrow 👍