Rollup merge of #150063 - workingjubilee:remove-let-else-deny, r=Kivooeo

Remove deny of manual-let-else

During discussion on Zulip[^1], we found there was no strong consensus in favor of this in practice.

[^1]: https://rust-lang.zulipchat.com/#narrow/channel/131828-t-compiler/topic/.60deny.28clippy.3A.3Amanual_let_else.29.60.20proliferation/with/564085588

Author: JonathanBrouwer