Fix manual challenge create

[col3zy]

When attempting to manually create a challenge the user is presented with a form consisting of:

• Name
• Points
• Category
• Description

On submit the api returns:
"Error: note_id. This field is required"
There is no option for the user to supply a note_id.

This is a validation error. note_id has a default which will be used for new challenges.

This PR removes note_id from the validation for ChallengeCreateForm.

[col3zy]

[DaniloNC]

It sounds like the new form check on template is false, even on new challenges.
I cannot see the HedgeDoc ID label in the html on a new challenge creation.

The note_id input is after the HedgeDoc ID.

ctfhub/ctfhub/templates/ctfhub/challenges/create.html

Lines 106 to 115 in 6d60501

	{% if form.instance.creation_time %}
	<label class="label"><strong>HedgeDoc ID </strong></label>
	<div class="input-group mb-3">
	<span class="input-group-text">
	<i class="fab fa-markdown"></i>
	</span>
	<input id="{{ form.note_id.id_for_label }}" name="{{ form.note_id.html_name }}"
	placeholder="{{ form.note_id.label }}" value="{{ form.note_id.value }}"
	class="form-control" type="text" readonly>
	</div>

[DaniloNC]

note_id not present during new challenge creation:

[col3zy]

Correct. It's only an option when editing an existing challenge (challenge.creation_time != null). Yet it's considered a mandatory field.