Audit log search - unexpected behavior

### How are you running Flagsmith

- [ ] Self Hosted with Docker
- [ ] Self Hosted with Kubernetes
- [ ] Self Hosted at flagsmith.com
- [X] Some other way (add details in description below)

### Describe the bug

The search in the audit log page is inconsistent.
The date column seems to be unsearchable.
Also the user column returns false search results.

### Steps To Reproduce

1. go to audit log page
2. enter a search term in the search text box
3. note that some existing strings are not found and some does
4. note that searching the date column is not possible

### Expected behavior

When searching for a string that is present in the audit log it should always return as a search result.
When searching for an existing date then the relevant audit log record should return as a search result.

### Screenshots