remove obsolete [CratesSize] test for null size

[jNullj]

Eliminate a test case that is no longer relevant due to upstream changes that removed all null crate sizes.

see also upstream merge that removed null for versions.crate_size upstream at rust-lang/crates.io#9926

[github-actions]

	Messages
📖	✨ Thanks for your contribution to Shields, @jNullj!

Generated by 🚫 dangerJS against 0c0b0b0

[chris48s]

If we don't expect to receive null sizes any more, then we shouldn't just delete the test. We should update/remove the application code that deals with that situation as well:

shields/services/crates/crates-base.js

Line 8 in 9447077

crate_size: nonNegativeInteger.allow(null),

shields/services/crates/crates-size.service.js

Lines 53 to 55 in 9447077

	if (size == null) {
	throw new InvalidResponse({ prettyMessage: 'unknown' })
	}