Inappropriate verbiage in the signals documentation

[cmaggiulli]

Describe the bug
In the documentation related to this projects signals the following text, "Sent before saving historical record", is printed by the pre_create_historical_record signal. However, this verbiage is wrong. It does not happen "before saving historical record". It happens before the creation of the historical record ( before the saving of the respective base object )".

I would like to change this verbiage to more accurately reflect whats happening.

To Reproduce
Steps to reproduce the behavior:

1. Navigate to https://django-simple-history.readthedocs.io/en/latest/signals.html
2. Read the description

Expected behavior
That code should execute before the creation of the historical record, not before "saving" the historical record

Screenshots
N/A

Environment (please complete the following information):
N/A

Additional context
Please allow me to make the fix as I'd like to start contributing to the project. I want to learn the contribution workflow. Ive already made the changes in this commit 8993d85

If anyone wants to suggest a different wording let me know and Ill update the PR. This actually caused confusion for me because I have the following code

@receiver(post_create_historical_record, sender=UnitRule.history.model)
def record_effective_end_date(sender, signal, instance, history_instance, **kwargs):

    time_of_change = timezone.now()

    history_instance.modified = time_of_change
    history_instance.save()

    if prev_instance := history_instance.prev_record:
	    prev_instance.effective_end_date=time_of_change
	    prev_instance.modified=time_of_change
	    prev_instance.save()

and I was concerned it was going to create an infinite loop based off the word "saving" in the example

[cmaggiulli]

If anyone has any recommendation for verbiage other than what is in my commit please post here