Don't try to delete index template along with pattern

[Bargs]

This commit reverts a change to use the ingest API when deleting index
patterns via the Kibana UI. Back when I was building the Filebeat wizard
it made sense to try to delete any index templates or pipelines that may
have been created along with an index pattern. But now that we're only
shipping with CSV Upload, and we don't delete the actual indices that
CSV upload creates, it doesn't make much sense to delete the template.
Now we'll treate the indices and templates consistently.

This also fixes an issue where users would get a fatal error if they
were using Security and they didn't have permissions to delete
templates. Every index pattern deletion would also attempt to delete an
associated template, so if the user didn't have the correct permissions
they would get a 403.

Related: #6457

[ycombinator]

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