Rollup merge of #66797 - mlodato517:mlodato517-array-doc-typo, r=Dylan-DPC

Fixes small typo in array docs r? @steveklabnik

Fixes a small typo in the array documentation.

Also, wasn't sure which [message](https://github.com/rust-lang/rust/blob/master/CONTRIBUTING.md#pull-requests) to put this in, and will definitely update the commit message if it is supposed to be the PR description but for "safety" - r? @steveklabnik