Bump io.papermc.paper:paper-api

Bumps io.papermc.paper:paper-api from 1.20.6-R0.1-SNAPSHOT to 1.21-R0.1-SNAPSHOT.

---
updated-dependencies:
- dependency-name: io.papermc.paper:paper-api
  dependency-type: direct:production
...

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

Author: dependabot[bot]

api/build.gradle.kts

@@ -23,7 +23,7 @@ repositories {
 dependencies {
     compileOnly("org.projectlombok:lombok:1.18.32")
     compileOnly("net.thenextlvl.core:annotations:2.0.1")
-    compileOnly("io.papermc.paper:paper-api:1.20.6-R0.1-SNAPSHOT")
+    compileOnly("io.papermc.paper:paper-api:1.21-R0.1-SNAPSHOT")
 
     compileOnlyApi(platform("com.intellectualsites.bom:bom-newest:1.45"))
     compileOnlyApi("com.fastasyncworldedit:FastAsyncWorldEdit-Bukkit")