Bump io.papermc.paper:paper-api in /paper

Bumps io.papermc.paper:paper-api from 1.21.1-R0.1-SNAPSHOT to 1.21.3-R0.1-SNAPSHOT.

---
updated-dependencies:
- dependency-name: io.papermc.paper:paper-api
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

paper/build.gradle.kts

@@ -25,7 +25,7 @@ repositories {
 
 dependencies {
     compileOnly("org.projectlombok:lombok:1.18.34")
-    compileOnly("io.papermc.paper:paper-api:1.21.1-R0.1-SNAPSHOT")
+    compileOnly("io.papermc.paper:paper-api:1.21.3-R0.1-SNAPSHOT")
     compileOnly(project(":annotations"))
 
     api(project(":version-checker")) {