Update documentation for Bazel 4.2.1 (#13558).

Closes #13922.

PiperOrigin-RevId: 393788736
diff --git a/scripts/docs/doc_versions.bzl b/scripts/docs/doc_versions.bzl
index 6407b99..58351ef 100644
--- a/scripts/docs/doc_versions.bzl
+++ b/scripts/docs/doc_versions.bzl
@@ -23,6 +23,10 @@
 
 DOC_VERSIONS = [
     {
+        "version": "4.2.1",
+        "sha256": "b767b7aa949f96b602257587add3be38acbead03bf919fe871397bc80d97f8b2",
+    },
+    {
         "version": "4.2.0",
         "sha256": "1188fc6c3354f85741bacbb2bc7dab6bbfd1d2f44475846293ff232fb01709b8",
     },
diff --git a/site/_config.yml b/site/_config.yml
index 050a3b4..0b258be 100644
--- a/site/_config.yml
+++ b/site/_config.yml
@@ -16,11 +16,12 @@
 url: "https://docs.bazel.build" # used by jekyll-sitemap
 
 # Update this to the newest release for the default docs.bazel.build version.
-version: "4.2.0"
+version: "4.2.1"
 
 # This must be kept in sync with //scripts/docs:doc_versions.bzl
 doc_versions:
   - main
+  - 4.2.1
   - 4.2.0
   - 4.1.0
   - 4.0.0