fix flaky basic outcomes spec
fix flaky basic outcomes spec

why:
* this spec runs just fine in rspec, but multiple runs in FSC make it
take longer and longer, up to 50 seconds
* run with custom_timeout as a stopgap
* investigate: why does run_jobs take longer and longer each run?

closes INTEROP-7163
flag=none

test plan
* Jenkins is happy

Change-Id: I993c807cc4c741a739c1a4f6c664c9a395b334c6
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/278984
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Tucker Mcknight <4b51b98c1d84aa97854d216bd061ce5d3eda8a28@instructure.com>
QA-Review: Tucker Mcknight <4b51b98c1d84aa97854d216bd061ce5d3eda8a28@instructure.com>
Product-Review: Xander Moffatt <27f70fe194da423604e6e0a63a3de19814736fa9@instructure.com>

sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms,sfu/canvas-lms