chore(dependencies): Autobump spinnakerGradleVersion (#1118)

Co-authored-by: root <root@cb8989fc1cab>

Author: spinnakerbot

gradle.properties

@@ -2,7 +2,7 @@ fiatVersion=1.28.0
 korkVersion=7.114.0
 kotlinVersion=1.4.0
 org.gradle.parallel=true
-spinnakerGradleVersion=8.14.0
+spinnakerGradleVersion=8.15.0
 targetJava11=true
 
 # To enable a composite reference to a project, set the