build(deps): bump multiplatform from 2.0.21 to 2.1.0 in /watermarker

Bumps [multiplatform](https://github.com/JetBrains/kotlin) from 2.0.21 to 2.1.0.
- [Release notes](https://github.com/JetBrains/kotlin/releases)
- [Changelog](https://github.com/JetBrains/kotlin/blob/v2.1.0/ChangeLog.md)
- [Commits](JetBrains/kotlin@v2.0.21...v2.1.0)

---
updated-dependencies:
- dependency-name: multiplatform
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

Signed-off-by: dependabot[bot] <[email protected]>

watermarker/build.gradle.kts

@@ -7,7 +7,7 @@
 import org.gradle.api.tasks.testing.logging.TestExceptionFormat
 
 plugins {
-    kotlin("multiplatform") version "2.0.21"
+    kotlin("multiplatform") version "2.1.0"
     id("maven-publish")
     id("org.jetbrains.dokka") version "1.9.20"
     id("org.jlleitschuh.gradle.ktlint") version "12.1.1"