Rollup merge of #68688 - jbr:remind-bug-reporters-to-update-if-on-nightly, r=centril
Rollup merge of #68688 - jbr:remind-bug-reporters-to-update-if-on-nightly, r=centril

[docs] remind bug reporters to update nightly

Hi and thanks for rust! Today I reported a bug in nightly that was already fixed, so I thought other potential bug reporters might appreciate a reminder to update before reporting.  I wasn't sure if this would apply for other channels as well.

graydon/rust,aidancully/rust,graydon/rust,aidancully/rust,aidancully/rust,aidancully/rust,graydon/rust,aidancully/rust,graydon/rust,graydon/rust,graydon/rust,aidancully/rust