Update dartdoc to 0.28.1+2 and fix search text alignment (#27559)

dev/bots/docs.sh

@@ -104,7 +104,7 @@ if [[ -d "$FLUTTER_PUB_CACHE" ]]; then
 fi
 
 # Install and activate dartdoc.
-"$PUB" global activate dartdoc 0.28.1+1
+"$PUB" global activate dartdoc 0.28.1+2
 
 # This script generates a unified doc set, and creates
 # a custom index.html, placing everything into dev/docs/doc.

dev/docs/assets/overrides.css

@@ -103,7 +103,6 @@ code {
   background-image: none;
   border: 1px solid #ccc;
   border-radius: 2px;
-  font-family: inherit;
   padding: 4px 6px;
   font-size: 15px;
 }