doc: add documentation-only deprecation for multiple Hmac.digest() calls (DEP0206)

Author: Anshikakalpana

doc/api/deprecations.md

@@ -4558,6 +4558,22 @@ that have proven unresolveable. See [caveats of asynchronous customization hooks
 `module.registerHooks()` as soon as possible as `module.register()` will be
 removed in a future version of Node.js.
 
+### DEP0206: Calling `digest()` on an already-finalized `Hmac` instance
+
+<!-- YAML
+changes:
+  - version: REPLACEME
+    pr-url: https://github.com/nodejs/node/pull/63121
+    description: Documentation-only deprecation.
+-->
+
+Type: Runtime
+
+Calling [`hmac.digest()`][] more than once returns an empty buffer instead of
+throwing an error. This behavior is inconsistent with [`hash.digest()`][] and
+may lead to subtle bugs. Calling `hmac.digest()` on a finalized `Hmac` instance
+will throw an error in a future version.
+
 [DEP0142]: #dep0142-repl_builtinlibs
 [NIST SP 800-38D]: https://nvlpubs.nist.gov/nistpubs/Legacy/SP/nistspecialpublication800-38d.pdf
 [RFC 6066]: https://tools.ietf.org/html/rfc6066#section-3