chore(tests): Enable dredd tests for event role permissions API

[blossom2017]

#7014

Short description of what this resolves:

Enables dredd tests for event role permissions API.

Changes proposed in this pull request:

Checklist

• I have read the Contribution & Best practices Guide and my PR follows them.
• My branch is up-to-date with the Upstream development branch.
• The unit tests pass locally with my changes
• I have added tests that prove my fix is effective or that my feature works
• I have added necessary documentation (if appropriate)

• All the functions created/modified in this PR contain relevant docstrings.

[houndci-bot]

module level import not at top of file

[houndci-bot]

Black would make changes.

[codecov]

Codecov Report

Merging #7231 into development will not change coverage.
The diff coverage is 100.00%.

@@             Coverage Diff              @@
##           development    #7231   +/-   ##
============================================
  Coverage        63.02%   63.02%           
============================================
  Files              259      259           
  Lines            13034    13034           
============================================
  Hits              8215     8215           
  Misses            4819     4819           

Impacted Files	Coverage Δ
app/api/schema/event_role_permissions.py	100.00% <100.00%> (ø)

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