[SE-4100] remove accidentally added git submodule

This PR removes the accidentally added git submodule from the submodules.

Dependencies: None

Screenshots: N/A

Sandbox URL: N/A

Merge deadline: None

Testing instructions:

1. git clone https://github.com/open-craft/opencraft/ test1
2. cd test1
3. git submodule
4. grep -r 'src/django-angular' .

Step 3 and 4 should not produce output.

Author notes and concerns:

N/A

Reviewers

• @mtyaka