Fix test_story_budget_set_number_days_filter_invalid in PHP 8.0

[htdat]

Fix #639

Description

Details here #639 (comment)
This PR should be merged after this PR #643 - actually, this PR is rebased on PR 643.

Steps to Test

1. Check out PR.
2. Set up WP test site bash bin/install-wp-tests.sh wordpress_test root root.
3. Run PHPUnit tests in PHP 8.0.x composer integration.
4. Confirm that all tests pass.

[mikeyarce]

Looking at the code, it looks like this is set to be (int) here:
https://github.com/Automattic/Edit-Flow/blob/124c3cde900c22abe15c04b0b2bd11e306b2aef4/modules/story-budget/story-budget.php#L201

However, in the test it doesn't look like we're casting as (int) here:
https://github.com/Automattic/Edit-Flow/blob/2e07a1b7b7af1e783b858700390da85b418c2405/tests/test-edit-flow-story-budget.php#L68

Instead of changing the code, would it make more sense to update the test to cast as (int)?

[htdat]

@mikeyarce

Looking at the code, it looks like this is set to be (int) here:
https://github.com/Automattic/Edit-Flow/blob/124c3cde900c22abe15c04b0b2bd11e306b2aef4/modules/story-budget/story-budget.php#L201

This is a good point!

However, in the test it doesn't look like we're casting as (int) here:
https://github.com/Automattic/Edit-Flow/blob/2e07a1b7b7af1e783b858700390da85b418c2405/tests/test-edit-flow-story-budget.php#L68
Instead of changing the code, would it make more sense to update the test to cast as (int)?

L68 here is already an int so I don't think we need to cast it.

However, actually, #639 mentions the error in other lines and test case:
https://github.com/Automattic/Edit-Flow/blob/2e07a1b7b7af1e783b858700390da85b418c2405/tests/test-edit-flow-story-budget.php#L88-L92

We can get rid of this test case but I think it's still good to keep this test and practice defensive coding for the EF_Story_Budget::update_user_filters_from_form_date_range_change method as it can be used somewhere else in the future?

[mikeyarce]

After discussion, this sounds like a good approach!