Allow creation date import (#16764)

PR for #15313 

<!-- CURSOR_SUMMARY -->
---

> [!NOTE]
> Enables importing timestamp fields that were previously filtered out.
> 
> - Removes explicit exclusions of `createdAt` and `updatedAt` in
`spreadsheetImportFilterAvailableFieldMetadataItems`
> - Keeps existing constraints: only active fields, system fields
limited (except `id`), exclude `deletedAt`, and only allow `RELATION`
fields that are `MANY_TO_ONE`; sorting unchanged
> 
> <sup>Written by [Cursor
Bugbot](https://cursor.com/dashboard?tab=bugbot) for commit
a2b36e4cc0473921edaabd9926e62228981b39e7. This will update automatically
on new commits. Configure
[here](https://cursor.com/dashboard?tab=bugbot).</sup>
<!-- /CURSOR_SUMMARY -->

---------

Co-authored-by: Félix Malfait <felix@twenty.com>

packages/twenty-front/src/modules/object-record/spreadsheet-import/utils/spreadsheetImportFilterAvailableFieldMetadataItems.ts

@@ -10,8 +10,6 @@ export const spreadsheetImportFilterAvailableFieldMetadataItems = (
       (fieldMetadataItem) =>
         fieldMetadataItem.isActive &&
         (!fieldMetadataItem.isSystem || fieldMetadataItem.name === 'id') &&
-        fieldMetadataItem.name !== 'createdAt' &&
-        fieldMetadataItem.name !== 'updatedAt' &&
         fieldMetadataItem.name !== 'deletedAt' &&
         (![FieldMetadataType.RELATION, FieldMetadataType.RICH_TEXT].includes(
           fieldMetadataItem.type,