Update plugin com.google.protobuf to v0.9.6

Author: renovate[bot]

settings.gradle.kts

@@ -1,6 +1,6 @@
 pluginManagement {
   plugins {
-    id("com.google.protobuf") version "0.9.5"
+    id("com.google.protobuf") version "0.9.6"
     id("de.undercouch.download") version "5.6.0"
     id("io.github.gradle-nexus.publish-plugin") version "2.0.0"
     id("org.gradle.toolchains.foojay-resolver-convention") version "1.0.0"