A case where rustbot assigned the PR author as the reviewer

[fmease]

In rust-lang/rust#103648, rustbot assigned the PR author as the reviewer.
CC @jyn514

There appears to be some code specifically to avoid this problem but for some reason it did not succeed in this situation:

triagebot/src/handlers/assign.rs

Lines 630 to 637 in ca14859

	let filter = |name: &&str| -> bool {
	let name_lower = name.to_lowercase();
	name_lower != issue.user.login.to_lowercase()
	&& !issue
	.assignees
	.iter()
	.any(|assignee| name_lower == assignee.login.to_lowercase())
	};