Ginkgo devsite: edx-drf-extensions 0.5.1 for edx-organizations compat

[bryanlandia]

Change description

Ginkgo devsite was using edx-drf-extensions 1.2.2 as used by edx-platform Ginkgo open-release, which is actually incompatible with the edx-drf-extensions required by edx-organizations 0.4.4. That must have broken install of Ginkgo.
For our use, go with the version required by 0.4.4. The only difference to edx-drf-extensions 1.2.2 is treatment of JWT tokens, which doesn't matter for Figures anyhow.

Allows Ginkgo tests to run via tox -e gingko

Type of change

• Bug fix (fixes an issue)
• New feature (adds functionality)

Checklists

Development

• Lint rules pass locally
• Application changes have been tested thoroughly
• Automated tests covering modified code pass

Security

• Security impact of change has been considered
• Code follows company security practices and guidelines

Code review

• Pull request has a descriptive title and context useful to a reviewer. Screenshots or screencasts are attached as necessary
• "Ready for review" label attached and reviewers assigned
• Changes have been reviewed by at least one other contributor
• Pull request linked to task tracker where applicable