Rollup merge of #80147 - pierwill:patch-9, r=lcnr
Rollup merge of #80147 - pierwill:patch-9, r=lcnr

Add missing punctuation to std::alloc docs

Add a period to first line of module docs to match other modules in std.

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