Update typeid-sql README.md (#376)

Corrects name of PostgreSQL in `README.md`

## Summary

1-line text change in `README.md`

## How was it tested?

n/a

Signed-off-by: Patrick Lewis <get@patricklewis.org>

typeid/typeid-sql/README.md

@@ -1,6 +1,6 @@
 # TypeID SQL
 
-### A SQL implementation of [TypeID](https://github.com/jetify-com/typeid) using PostgresSQL.
+### A SQL implementation of [TypeID](https://github.com/jetify-com/typeid) using PostgreSQL.
 
 ![License: Apache 2.0](https://img.shields.io/github/license/jetify-com/typeid-sql)