Disallow Importing Stratification Factors for Users with the 'Reader' Role

[zackcl]

Version where bug was found:
6.0.0

Describe the bug
We should not allow importing stratification factors for users with the 'Reader' role.

To Reproduce
Steps to reproduce the behavior:

1. Go to the Profile page and update your role to 'Reader' (note: not sure how to revert to 'Admin' later though).
2. Go to the Participants page and click the "Stratifications" tab.
3. Observe that the "Import CSV" button is visible and clickable.

Expected behavior
The "Import CSV" button above the Stratifications table should be invisible for users with the 'Reader' role.

Screenshots

Additional context
Related Issue: #1998

[danoswaltCL]

I will QA

[danoswaltCL]

passed