Creating or Updating access plans when there are 6 (max) plans associated with a course/membership results in errors

[thomasplevy]

Reproduction Steps

• Create a course with 6 access plans
• Attempt to update one of the 6 plans via the REST API

Expected Behavior

• The plan updates

Actual Behavior

• A validation error is encountered: 'Only 6 access plans allowed per course

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This method appears to correctly validate against creating a new plan when the limit has been reached but it's also preventing any edits of existing plans when the limit has been reached.