Remove error state on title field (#227098)

## Summary

Closes #224820

Remove error state for name field when creating a new knowledge base
entry.

I consulted with @isaclfreire offline about this change and we agreed to
remove the error state completely, as error states are not necessary in
cases where all fields in a form are mandatory in order to continue.

### Before


https://github.com/user-attachments/assets/32aab4ad-e558-4e9c-b9c1-b54e9e20b362

### After


https://github.com/user-attachments/assets/4b873397-66fc-4b9c-be0c-dc118e54bfc9

### Checklist

Check the PR satisfies following conditions. 

Reviewers should verify this PR satisfies this list as well.

- [x] The PR description includes the appropriate Release Notes section,
and the correct `release_note:*` label is applied per the
[guidelines](https://www.elastic.co/guide/en/kibana/master/contributing.html#kibana-release-notes-process)
- [x] Review the [backport
guidelines](https://docs.google.com/document/d/1VyN5k91e5OVumlc0Gb9RPa3h1ewuPE705nRtioPiTvY/edit?usp=sharing)
and apply applicable `backport:*` labels.

Author: eleonoramicozzi

x-pack/platform/plugins/private/observability_ai_assistant_management/public/routes/components/knowledge_base_edit_manual_entry_flyout.tsx

@@ -140,7 +140,6 @@ export function KnowledgeBaseEditManualEntryFlyout({
             fullWidth
             value={newEntryTitle}
             onChange={(e) => setNewEntryTitle(e.target.value)}
-            isInvalid={isEntryTitleInvalid}
           />
         </EuiFormRow>