Upgrade dartdoc to v0.14.1 (#12420)

dev/bots/docs.sh

diff --git a/dev/bots/docs.sh b/dev/bots/docs.sh
index 3ac5ec3..4d9aaab 100755
--- a/dev/bots/docs.sh
+++ b/dev/bots/docs.sh
@@ -10,7 +10,7 @@
 bin/flutter --version
 
 # Install dartdoc.
-bin/cache/dart-sdk/bin/pub global activate dartdoc 0.13.0+3
+bin/cache/dart-sdk/bin/pub global activate dartdoc 0.14.1
 
 # This script generates a unified doc set, and creates
 # a custom index.html, placing everything into dev/docs/doc.