Replace emoji.json link in markdown docstring with Streamlit app (#4396)

lib/streamlit/elements/markdown.py

@@ -34,7 +34,7 @@ def markdown(self, body, unsafe_allow_html=False):
 
             * Emoji shortcodes, such as `:+1:`  and `:sunglasses:`.
               For a list of all supported codes,
-              see https://raw.githubusercontent.com/omnidan/node-emoji/master/lib/emoji.json.
+              see https://share.streamlit.io/streamlit/emoji-shortcodes.
 
             * LaTeX expressions, by wrapping them in "$" or "$$" (the "$$"
               must be on their own lines). Supported LaTeX functions are listed