Fix incorrect message displayed on importing Timeline Templates (elas…

…tic#101288)

Context:
The import button can be used to import both timelines and timeline templates.
In theory, one imported file could have multiple timelines and timeline templates at the same time.

Solution:
Since the import endpoint only returns the total count and not the type of the imported documents.
It seems like that rewording "timeline(s)" to "item(s)" is the most straightforward fix that solves
the user problem.

Co-authored-by: Kibana Machine <42973632+kibanamachine@users.noreply.github.com>

x-pack/plugins/security_solution/public/timelines/components/open_timeline/translations.ts

@@ -369,7 +369,7 @@ export const SUCCESSFULLY_IMPORTED_TIMELINES = (totalCount: number) =>
     {
       values: { totalCount },
       defaultMessage:
-        'Successfully imported {totalCount} {totalCount, plural, =1 {timeline} other {timelines}}',
+        'Successfully imported {totalCount} {totalCount, plural, =1 {item} other {items}}',
     }
   );