Fix README.md (#1209)

update quickstart links for Cloud Storage and Firebase Alerts

Author: kimyubin

README.md

@@ -59,9 +59,9 @@ This quickstart demonstrates using **Cloud Functions** with an HTTPS trigger tha
 
 ### Cloud Storage trigger quickstart: Thumbnail generator
 
-- [Node 2nd gen](/Node/quickstarts/https-time-server/)
-- [Python](/Python/quickstarts/https-time-server/)
-- [Node 1st gen](/Node-1st-gen/quickstarts/https-time-server/)
+- [Node 2nd gen](/Node/quickstarts/thumbnails/)
+- [Python](/Python/quickstarts/thumbnails/)
+- [Node 1st gen](/Node-1st-gen/quickstarts/thumbnails/)
 
 This quickstart sample demonstrates using **Cloud Functions** triggered by **Firebase Storage events**. The function generates a thumbnail of uploaded images.
 
@@ -94,7 +94,7 @@ This quickstart sample demonstrates using **Cloud Functions** triggered by **Pub
 - [Node 2nd gen](/Node/quickstarts/testlab-matrix-completed/)
 - [Python](/Python/quickstarts/testlab-matrix-completed/)
 
-### Firebase Alerts trigger quickstart: Send crash reports to Discord](/2nd-gen/alerts-to-discord/)
+### Firebase Alerts trigger quickstart: Send crash reports to Discord
 
 - [Node 2nd gen](/Node/alerts-to-discord/)
 - [Python](/Python/alerts-to-discord/)