Rev dartdoc to 6.1.2 (#112664)

diff --git a/dev/bots/docs.sh b/dev/bots/docs.sh
index 0f95f14..5569d50 100755
--- a/dev/bots/docs.sh
+++ b/dev/bots/docs.sh
@@ -20,7 +20,7 @@
     # Install and activate dartdoc.
     # NOTE: When updating to a new dartdoc version, please also update
     # `dartdoc_options.yaml` to include newly introduced error and warning types.
-    "$DART" pub global activate dartdoc 6.1.1
+    "$DART" pub global activate dartdoc 6.1.2
 
     # Install and activate the snippets tool, which resides in the
     # assets-for-api-docs repo: