Update plugin spotless to v6.9.1 (#3425)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

gradle/libs.versions.toml

@@ -90,7 +90,7 @@ dokka = { id = "org.jetbrains.dokka", version.ref = "dokka" }
 intellij = { id = "org.jetbrains.intellij", version = "1.6.0" }
 grammarKitComposer = { id = "com.alecstrong.grammar.kit.composer", version = "0.1.10" }
 publish = { id = "com.vanniktech.maven.publish", version = "0.21.0" }
-spotless = { id = "com.diffplug.spotless", version = "6.9.0" }
+spotless = { id = "com.diffplug.spotless", version = "6.9.1" }
 changelog = { id = "org.jetbrains.changelog", version = "1.3.1" }
 shadow = { id = "com.github.johnrengelman.shadow", version = "7.1.2" }
 ksp = { id = "com.google.devtools.ksp", version = "1.7.10-1.0.6" }