chore(deps): update plugin javadoclinks to v0.0.21

Author: renovate[bot]

gradle/libs.versions.toml

@@ -28,4 +28,4 @@ gradle-plugin-javadocLinks = "org.incendo.cloud-build-logic.javadoc-links:org.in
 indra = { id = "net.kyori.indra", version.ref = "indra" }
 indraCheckstyle = { id = "net.kyori.indra.checkstyle", version.ref = "indra" }
 indraPublishing = { id = "net.kyori.indra.publishing", version.ref = "indra" }
-javadocLinks = { id = "org.incendo.cloud-build-logic.javadoc-links", version = "0.0.18" }
+javadocLinks = { id = "org.incendo.cloud-build-logic.javadoc-links", version = "0.0.21" }