fix(redhat-openshift.md): use correct env var name

[falko]

I tested together with a prospect in their Open Shift cluster that this is the right configuration.

Description

When should this change go live?

• This change is not yet live and should not be merged until {ADD_DATE} (apply hold label or convert to draft PR)?
• There is no urgency with this change.
• This change or page is part of a marketing blog, conference talk, or something else on a schedule.
• This functionality is already available but undocumented.
• This is a bug fix or security concern.

PR Checklist

• I have added changes to the relevant /versioned_docs directory, or they are not for an already released version.
• I have added changes to the main /docs directory (aka /next/), or they are not for future versions.
• My changes require an Engineering review, and I've assigned an engineering manager or tech lead as a reviewer, or my changes do not require an Engineering review.
• My changes require a technical writer review, and I've assigned @christinaausley as a reviewer, or my changes do not require a technical writer review.

[falko]

This needs backporting to all versions.

[falko]

@christinaausley anything else you need from me?

[akeller]

@camunda/distribution can you confirm these changes are correct?

[aabouzaid]

@akeller that should be reviewed by the Operate/Tasklist team since it's app config.

[akeller]

@johanwelgemoed @marcosgvieira can you confirm these environment variables are correct for Operate and Tasklist config?

[johanwelgemoed]

@akeller Looked at it together with Svetlana, she approved from Operate side.

[marcosgvieira]

I confirm that this is correct.

[akeller]

Thank you, everyone!