build(deps): bump dev.sigstore.sign from 0.8.0 to 0.9.0 in /java

Bumps dev.sigstore.sign from 0.8.0 to 0.9.0.

---
updated-dependencies:
- dependency-name: dev.sigstore.sign
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <support@github.com>

java/build.gradle.kts

@@ -1,7 +1,7 @@
 plugins {
     `java-library`
     `maven-publish`
-    id("dev.sigstore.sign") version "0.8.0"
+    id("dev.sigstore.sign") version "0.9.0"
     id("com.diffplug.spotless") version "6.25.0"
     `signing`
 }