rubocop config tweaks
rubocop config tweaks

 * instead of turning Lint/AmbiguousBlockAssociation off for specs,
   just ignore it for the specific spec methods that it's commonly
   allowed

see comments in config for other changes

Change-Id: I73b1c404294c37b72ff6a14aac557abf8f3f9a2f
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/275453
Tested-by: Service Cloud Jenkins <9144042a601061f88f1e1d7a1753ea3e2972119d@instructure.com>
Reviewed-by: Simon Williams <088e16a1019277b15d58faf0541e11910eb756f6@instructure.com>
QA-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>
Product-Review: Cody Cutrer <c4fe2b1d90ef8f2548c8aeabfa633434316f0305@instructure.com>

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