Bump org.spigotmc:spigot-api

Bumps org.spigotmc:spigot-api from 1.21.2-R0.1-SNAPSHOT to 1.21.3-R0.1-SNAPSHOT.

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

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

build.gradle

@@ -33,7 +33,7 @@ repositories {
 dependencies {
     compileOnly 'org.jetbrains:annotations:26.0.1'
 
-    compileOnly 'org.spigotmc:spigot-api:1.21.2-R0.1-SNAPSHOT'
+    compileOnly 'org.spigotmc:spigot-api:1.21.3-R0.1-SNAPSHOT'
     implementation 'org.bstats:bstats-bukkit:3.1.0'
 
     compileOnly group: "com.comphenix.protocol", name: "ProtocolLib", version: "5.1.0"