Bump com.google.devtools.ksp from 1.8.10-1.0.9 to 1.9.21-1.0.15

Bumps [com.google.devtools.ksp](https://github.com/google/ksp) from 1.8.10-1.0.9 to 1.9.21-1.0.15.
- [Release notes](https://github.com/google/ksp/releases)
- [Commits](google/ksp@1.8.10-1.0.9...1.9.21-1.0.15)

---
updated-dependencies:
- dependency-name: com.google.devtools.ksp
  dependency-type: direct:production
  update-type: version-update:semver-minor
...

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

build.gradle.kts

@@ -6,5 +6,5 @@ plugins {
     id("com.android.library") version "8.0.1" apply false
     id("org.jetbrains.kotlin.android") version "1.8.10" apply false
     id("org.jetbrains.kotlin.plugin.serialization") version "1.8.10"
-    id("com.google.devtools.ksp") version "1.8.10-1.0.9" apply false
+    id("com.google.devtools.ksp") version "1.9.21-1.0.15" apply false
 }