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`.
James Rodewig
James Rodewig
Andrei Dan
Dan Hermann