Auto merge of #36557 - sfackler:fix-hashdos-docs, r=alexcrichton
Auto merge of #36557 - sfackler:fix-hashdos-docs, r=alexcrichton

Clean up hasher discussion on HashMap

* We never want to make guarantees about protecting against attacks.
* "True randomness" is not the right terminology to be using in this
    context.
* There is significantly more nuance to the performance of SipHash than
    "somewhat slow".

r? @steveklabnik

Follow up to discussion on #35371

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