Unrolled build for #144569

Rollup merge of #144569 - tshepang:rdg-sync, r=Kobzol

rustc-dev-guide subtree update

Subtree update of `rustc-dev-guide` to rust-lang/rustc-dev-guide@e19866a.

Created using https://github.com/rust-lang/josh-sync.

r? `````@ghost`````

Author: rust-timer

src/doc/rustc-dev-guide/rust-version

@@ -1 +1 @@
-efd420c770bb179537c01063e98cb6990c439654
+2b5e239c6b86cde974b0ef0f8e23754fb08ff3c5

src/doc/rustc-dev-guide/src/SUMMARY.md

@@ -53,7 +53,8 @@
 - [Walkthrough: a typical contribution](./walkthrough.md)
 - [Implementing new language features](./implementing_new_features.md)
 - [Stability attributes](./stability.md)
-- [Stabilizing Features](./stabilization_guide.md)
+- [Stabilizing language features](./stabilization_guide.md)
+    - [Stabilization report template](./stabilization_report_template.md)
 - [Feature Gates](./feature-gates.md)
 - [Coding conventions](./conventions.md)
 - [Procedures for breaking changes](./bug-fix-procedure.md)