Bump org.spigotmc:spigot-api (#7)

Bumps org.spigotmc:spigot-api from 1.18-R0.1-SNAPSHOT to 1.20.4-R0.1-SNAPSHOT.

---
updated-dependencies:
- dependency-name: org.spigotmc:spigot-api
  dependency-type: direct:production
...

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Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

build.gradle.kts

@@ -32,7 +32,7 @@ dependencies {
 
     // Other dependencies that are not required or already available at runtime
     compileOnly("org.projectlombok:lombok:1.18.30")
-    compileOnly("org.spigotmc:spigot-api:1.18-R0.1-SNAPSHOT")
+    compileOnly("org.spigotmc:spigot-api:1.20.4-R0.1-SNAPSHOT")
 
     // Enable lombok annotation processing
     annotationProcessor("org.projectlombok:lombok:1.18.30")