Rollup merge of #69861 - Dylnuge:dylnuge/locale-doc, r=Mark-Simulacrum
Rollup merge of #69861 - Dylnuge:dylnuge/locale-doc, r=Mark-Simulacrum

Add note about localization to std::fmt docs

Closes #69681

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