github: Remove issue template and use central one

Remove the GitHub issue template from this repository. We already have a
central set of templates [1] that are being used so the template in this
repository is redundant.

[1] - https://github.com/kata-containers/.github/tree/master/.github/ISSUE_TEMPLATE/

Fixes: kata-containers#846.

Signed-off-by: James O. D. Hunt <james.o.hunt@intel.com>