Roll dartdoc to 9.0.0 (#177590)
Required for compatibility with the latest Dart SDK and analyzer package
diff --git a/dev/bots/docs.sh b/dev/bots/docs.sh
index c69b34b..014faff 100755
--- a/dev/bots/docs.sh
+++ b/dev/bots/docs.sh
@@ -121,7 +121,7 @@
# Install and activate dartdoc.
# When updating to a new dartdoc version, please also update
# `dartdoc_options.yaml` to include newly introduced error and warning types.
- "$DART" pub global activate dartdoc 8.3.3
+ "$DART" pub global activate dartdoc 9.0.0
# Build and install the snippets tool, which resides in
# the dev/docs/snippets directory.