Fix a simple typo
Fix rustc panic on second compile_input
auto merge of #19401 : MatejLach/rust/guide_are_fix, r=steveklabnik

Fixes a small omission of `are` in the sentence:
`There also a few things you can do with a tuple as a whole, without...`
r @steveklabnik?
auto merge of #19392 : murarth/rust/rustc-compile-twice, r=nick29581

Closes #19371