Fix Keycloak capitalization

[ahus1]

Description

Documentation compilation

• Verified that documentation compiles without warnings.

(I'll rely on GitHub actions to perform that test)

Changelog

• Updated CHANGELOG.md.

(I wouldn't add this to the changelog, please let me know if this isn't the case)

Code formatting & web optimization

• Added or updated meta descriptions.
• Updated redirects.js if necessary (guide).
• Used three-space indentation in .rst files.

(not changed)

Writing style

• Used bold for UI elements, italics for key terms or emphasis, and code font for Bash commands, file names, REST paths, and code.
• Followed present tense, active voice, and a semi-formal tone.
• Wrote short, clear, and concise sentences.

(not changed)

[ahus1]

About "Verified that documentation compiles without warnings." - I didn't see any automation in GitHub actions run here, so I just assume those minimal changes are ok.

[ahus1]

I've now updated the PR to target 4.12.0, but from reading the CONTRIBUTING.md file I don't really know which branch to choose. Please advise.