fix(deps): update dependency com.diffplug.spotless:spotless-plugin-gradle to v8 (#808)

Co-authored-by: elastic-renovate-prod[bot] <174716857+elastic-renovate-prod[bot]@users.noreply.github.com>

Author: elastic-renovate-prod[bot]

gradle/libs.versions.toml

@@ -1,7 +1,7 @@
 [versions]
 shadow = "9.1.0"
 jib = "3.4.5"
-spotless = "7.2.1"
+spotless = "8.0.0"
 junit = "5.13.4"
 autoservice = "1.1.1"
 log4j2 = "2.25.2"