message: Document stabilization version
diff: @@ -1437,3 +1437,10 @@ serde = "1.0.117"
  [profile.dev.package.foo]
  codegen-backend = "cranelift"
  ```
  +
  +### patch-in-config
  +
  +The `-Z patch-in-config` flag, and the corresponding support for
  +`[patch]` section in Cargo configuration files has been stabilized in
  +the 1.56 release. See the [patch field](config.html#patch) for more
  +information.
  