Removes the `@timestamp` field mapping from several data stream index
template snippets.
With #59317, the `@timestamp` field defaults to a `date` field data type
for data streams.
This makes the data_stream timestamp field specification optional when
defining a composable template.
When there isn't one specified it will default to `@timestamp`.
(cherry picked from commit 5609353c5d164e15a636c22019c9c17fa98aac30)
Signed-off-by: Andrei Dan <andrei.dan@elastic.co>
James Rodewig
Andrei Dan
Dan Hermann