fix(integrations) Don't fail on a missing external issue (#10492)
fix(integrations) Don't fail on a missing external issue (#10492)

External issues could be deleted while queue jobs are in-flight. Instead
of failing we can just skip the sync work.

Fixes SENTRY-85J
beeftornado/sentry,mvaled/sentry,mvaled/sentry,mvaled/sentry,beeftornado/sentry,mvaled/sentry,mvaled/sentry,beeftornado/sentry,mvaled/sentry