Fix real mem doc

[berland]

Issue Resolves REALIZATION_MEMORY not listed in keyword overview table.

Approach ➕

• [x] PR title captures the intent of the changes, and is fitting for release notes.
• [x] Added appropriate release note label
• [x] Commit history is consistent and clean, in line with the contribution guidelines.
• [x] 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

• [x] 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 :white_check_mark:

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

:white_check_mark: All tests successful. No failed tests found.

Additional details and impacted files

```diff @@ 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](https://app.codecov.io/gh/equinor/ert/pull/8837/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor) | Coverage Δ | | |---|---|---| | [cli-tests](https://app.codecov.io/gh/equinor/ert/pull/8837/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor) | `39.62% <ø> (+0.01%)` | :arrow_up: | | [gui-tests](https://app.codecov.io/gh/equinor/ert/pull/8837/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor) | `73.58% <ø> (ø)` | | | [performance-tests](https://app.codecov.io/gh/equinor/ert/pull/8837/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor) | `50.05% <ø> (ø)` | | | [unit-tests](https://app.codecov.io/gh/equinor/ert/pull/8837/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor) | `79.84% <ø> (+0.02%)` | :arrow_up: | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=equinor#carryforward-flags-in-the-pull-request-comment) to find out more.

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