findmissing: Update supported branches

Replace 5.7 and 5.8 stable branches with 5.10, and add chromeos-5.10.

Unrelated change mandated by repo:
- Handle "Consider explicitly re-raising using the 'from' keyword"

BUG=None
TEST=Run tool and verify that 5.10 is supported

Change-Id: I96bb01549e200b69743a479daa06f01e79b0fefc
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/dev-util/+/2606646
Reviewed-by: Curtis Malainey <cujomalainey@chromium.org>
Commit-Queue: Guenter Roeck <groeck@chromium.org>
Tested-by: Guenter Roeck <groeck@chromium.org>
1 file changed