doc: fix added: info for outgoingMessage.{,un}cork()

`outgoingMessage.cork()` and `outgoingMessage.uncork()` were added to
Node.js v13.2.0 via 62e15a793a and backported to Node.js v12.16.0 via
db8144be31.

PR-URL: https://github.com/nodejs/node/pull/42711
Reviewed-By: Paolo Insogna <paolo@cowtech.it>
Reviewed-By: Antoine du Hamel <duhamelantoine1995@gmail.com>
Reviewed-By: Akhil Marsonya <akhil.marsonya27@gmail.com>
Reviewed-By: Mestery <mestery@protonmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

doc/api/http.md

@@ -2507,7 +2507,9 @@ Aliases of `outgoingMessage.socket`
 ### `outgoingMessage.cork()`
 
 <!-- YAML
-added: v14.0.0
+added:
+  - v13.2.0
+  - v12.16.0
 -->
 
 See [`writable.cork()`][].
@@ -2713,7 +2715,9 @@ After calling `outgoingMessage.end()`, this property will be nulled.
 ### `outgoingMessage.uncork()`
 
 <!-- YAML
-added: v14.0.0
+added:
+  - v13.2.0
+  - v12.16.0
 -->
 
 See [`writable.uncork()`][]