chore(dependencies): bump spinnakerGradleVersion (#4251)

to pick up google artifact registry publishing fixes

Doing this manually rather than backporting ~7 PRs

Co-authored-by: mergify[bot] <37929162+mergify[bot]@users.noreply.github.com>

gradle.properties

@@ -2,7 +2,7 @@ fiatVersion=1.28.0
 korkVersion=7.115.2
 kotlinVersion=1.4.32
 org.gradle.parallel=true
-spinnakerGradleVersion=8.15.0
+spinnakerGradleVersion=8.23.0
 targetJava11=true
 
 # To enable a composite reference to a project, set the