docs: update license badge link to main branch

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: rbygrave

README.md

@@ -1,6 +1,6 @@
 [![Build](https://github.com/ebean-orm/ebean-datasource/actions/workflows/build.yml/badge.svg)](https://github.com/ebean-orm/ebean-datasource/actions/workflows/build.yml)
 [![Maven Central : ebean](https://maven-badges.herokuapp.com/maven-central/io.ebean/ebean-datasource/badge.svg)](https://maven-badges.herokuapp.com/maven-central/io.ebean/ebean-datasource)
-[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://github.com/ebean-orm/ebean-datasource/blob/master/LICENSE)
+[![License](https://img.shields.io/badge/License-Apache%202.0-blue.svg)](https://github.com/ebean-orm/ebean-datasource/blob/main/LICENSE)
 [![JDK EA](https://github.com/ebean-orm/ebean-datasource/actions/workflows/jdk-ea.yml/badge.svg)](https://github.com/ebean-orm/ebean-datasource/actions/workflows/jdk-ea.yml)
 
 # ebean-datasource