[gradle dependency]: Bump org.slf4j:slf4j-api from 2.0.13 to 2.0.15

Bumps org.slf4j:slf4j-api from 2.0.13 to 2.0.15.

---
updated-dependencies:
- dependency-name: org.slf4j:slf4j-api
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

build.gradle.kts

@@ -21,7 +21,7 @@ dependencies {
     // https://mvnrepository.com/artifact/ch.qos.logback/logback-classic
     implementation("ch.qos.logback:logback-classic:1.5.6")
     // https://mvnrepository.com/artifact/org.slf4j/slf4j-api
-    implementation("org.slf4j:slf4j-api:2.0.13")
+    implementation("org.slf4j:slf4j-api:2.0.15")
 
     //test
     testImplementation(kotlin("test"))