Fix version override: Use edx-sga 0.22.0 via appsembler.txt reqs

[bryanlandia]

Change description

edx-sga in EDXAPP_EXTRA_REQUIREMENTS via server-vars.yml wasn't overriding the one defined in requirements/edx/appsembler.txt. Define it directly in our pip requirements.

Type of change

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

Related issues

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

[github-actions]

Checking git merge conflicts against https://github.com/edx/edx-platform.git

Comparing with	open-release/nutmeg.master
Benchmark conflicts with main	299
Current conflicts	299
Summary	Good work! No added conflicts.

Comparing with	master
Benchmark conflicts with main	312
Current conflicts	312
Summary	Good work! No added conflicts.