Updated the 2.1.3 Release Notes to capitalize STS

Author: Brendan Lynch

README.md

@@ -147,7 +147,7 @@ all languages.
 ## Release Notes
 
 ### Release 2.1.3 (August 8, 2023)
-* Added the ability to specify sts endpoint and region [PR #221](https://github.com/awslabs/amazon-kinesis-client-python/pull/230)
+* Added the ability to specify STS endpoint and region [PR #221](https://github.com/awslabs/amazon-kinesis-client-python/pull/230)
 * Upgraded KCL and KCL-Multilang Dependencies from 2.5.1 to 2.5.2 [PR #221](https://github.com/awslabs/amazon-kinesis-client-python/pull/230)
 
 ### Release 2.1.2 (June 29, 2023)