remove total grade tooltip when groups are weighted

fixes CNVS-10777

test plan:
- As teacher go to GB2
  - When assignment groups are weighted, total grade should not have a tooltip
  - When assignment groups are not weighted, tooltip should display normally
- As a student to to grade summary page
  - When assignment groups are weighted, total grade should not have a tooltip
  - When assignment groups are not weighted, tooltip should display normally

Change-Id: I80db6ddfff15116a2660e387fc517149cfc0f602
Reviewed-on: https://gerrit.instructure.com/29279
Reviewed-by: Matthew Irish <mirish@instructure.com>
Tested-by: Jenkins <jenkins@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>
Product-Review: Mike Nomitch <mnomitch@instructure.com>