Use SPDX identifier for license (#20)

Author: martinbonnin

librarian.root.properties

@@ -13,7 +13,7 @@ pom.groupId=com.apollographql.mockserver
 pom.description=KMP ready HTTP mock server
 pom.vcsUrl=https://github.com/apollographql/apollo-kotlin-mockserver
 pom.developer=Apollo Kotlin Mockserver contributors
-pom.license=MIT License
+pom.license=MIT
 
 gcs.bucket=apollo-snapshots
 gcs.prefix=m2