Fixed syntax error in docs.

Author: jonathanslenders

docs/pages/asking_for_input.rst

@@ -656,7 +656,7 @@ of the foreground.
     from prompt_toolkit.formatted_text import HTML
 
     def bottom_toolbar():
-        return HTML("This is a <b><style bg="ansired">Toolbar</style></b>!")
+        return HTML('This is a <b><style bg="ansired">Toolbar</style></b>!')
 
     text = prompt("> ", bottom_toolbar=bottom_toolbar)
     print(f"You said: {text}")