chore: remove sponsorship ask (#954)

Author: kiwicopple

README.md

@@ -116,9 +116,3 @@ To use your own database connection string instead of the provided test database
 
 Apache 2.0
 
-## Sponsors
-
-We are building the features of Firebase using enterprise-grade, open source products. We support existing communities wherever possible, and if the products don’t exist we build them and open source them ourselves.
-
-[![New Sponsor](https://user-images.githubusercontent.com/10214025/90518111-e74bbb00-e198-11ea-8f88-c9e3c1aa4b5b.png)](https://github.com/sponsors/supabase)
-