Update to oauth2-oidc-sdk 6.8

Fixes gh-6782

Author: jgrandja

gradle/dependency-management.gradle

@@ -55,7 +55,7 @@ dependencyManagement {
 		dependency 'com.google.inject:guice:3.0'
 		dependency 'com.nimbusds:lang-tag:1.4.3'
 		dependency 'com.nimbusds:nimbus-jose-jwt:7.0.1'
-		dependency 'com.nimbusds:oauth2-oidc-sdk:6.5'
+		dependency 'com.nimbusds:oauth2-oidc-sdk:6.8'
 		dependency 'com.squareup.okhttp3:okhttp:3.12.2'
 		dependency 'com.squareup.okio:okio:1.13.0'
 		dependency 'com.sun.xml.bind:jaxb-core:2.3.0.1'