.github: update ISSUE_TEMPLATE to be closer to 'go bug'

.github: update ISSUE_TEMPLATE to be closer to 'go bug'

Ask whether the issue reproduces with the latest release.

'go bug' places the version and system details last,
in part because they're automatically filled.
I'd like to do the same here, but I worry
that they'll get ignored.

Change-Id: Iec636a27e6e36d61dca421deaf24ed6fe35d4b11
Reviewed-on: https://go-review.googlesource.com/50931
Reviewed-by: Emmanuel Odeke <emm.odeke@gmail.com>
Reviewed-by: Daniel Martí <mvdan@mvdan.cc>
Reviewed-by: Avelino <t@avelino.xxx>