Fix real mem doc

[berland]

Issue
Resolves REALIZATION_MEMORY not listed in keyword overview table.

Approach
➕

• PR title captures the intent of the changes, and is fitting for release notes.
• Added appropriate release note label
• Commit history is consistent and clean, in line with the contribution guidelines.
• Make sure unit tests pass locally after every commit (git rebase -i main --exec 'pytest tests/ert/unit_tests -n logical -m "not integration_test"')

When applicable

• When there are user facing changes: Updated documentation
• New behavior or changes to existing untested code: Ensured that unit tests are added (See Ground Rules).
• Large PR: Prepare changes in small commits for more convenient review
• Bug fix: Add regression test for the bug
• Bug fix: Create Backport PR to latest release

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 91.40%. Comparing base (9f8d73a) to head (6de07f9).
Report is 7 commits behind head on main.

✅ All tests successful. No failed tests found.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #8837      +/-   ##
==========================================
+ Coverage   91.37%   91.40%   +0.02%     
==========================================
  Files         342      342              
  Lines       21028    21028              
==========================================
+ Hits        19215    19221       +6     
+ Misses       1813     1807       -6     

Flag	Coverage Δ
cli-tests	39.62% <ø> (+0.01%)	⬆️
gui-tests	73.58% <ø> (ø)
performance-tests	50.05% <ø> (ø)
unit-tests	79.84% <ø> (+0.02%)	⬆️

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[eivindjahren]

👍