Rollup merge of #63743 - alexcrichton:allow-lock-merge, r=Mark-Simulacrum
Rollup merge of #63743 - alexcrichton:allow-lock-merge, r=Mark-Simulacrum

Allow git to merge `Cargo.lock`

This commit backs out #46539 in order to fully leverage #63579 where
`git` should be able to merge `Cargo.lock` nowadays with only minimal
conflicts.

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