Auto merge of #64904 - ollie27:rustdoc_logo, r=Mark-Simulacrum
Auto merge of #64904 - ollie27:rustdoc_logo, r=Mark-Simulacrum

rustdoc: Fix default logo filename

This was a typo made in #64443. It's the reason the logo is missing on the [nightly docs](https://doc.rust-lang.org/nightly/std/).

r? @Mark-Simulacrum

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