Auto merge of #2115 - rust-lang:comment_nit, r=oli-obk
Auto merge of #2115 - rust-lang:comment_nit, r=oli-obk

Update a path to libstd source in our comments

Taken from review in https://github.com/rust-lang/miri/pull/2101

rust-lang/miri,rust-lang/miri,rust-lang/miri,rust-lang/miri