github: switch seen/expected order in issue forms

github: switch seen/expected order in issue forms

Also fixup wording across other templates.

Fixes #64890

Change-Id: I6f9ade440b6702ddfafc21ccb7fbc6cabc2b856e
Reviewed-on: https://go-review.googlesource.com/c/go/+/553155
Auto-Submit: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Joseph Tsai <joetsai@digital-static.net>
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@golang.org>
Reviewed-by: Bryan Mills <bcmills@google.com>
Reviewed-by: Dmitri Shuralyov <dmitshur@google.com>