Bump spigot-api from 1.17.1-R0.1-SNAPSHOT to 1.18-R0.1-SNAPSHOT (#376)

Bumps spigot-api from 1.17.1-R0.1-SNAPSHOT to 1.18-R0.1-SNAPSHOT.

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

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mywarp-bukkit/build.gradle

@@ -17,7 +17,7 @@ repositories {
 
 dependencies {
     implementation project(":mywarp-core")
-    implementation "org.spigotmc:spigot-api:1.17.1-R0.1-SNAPSHOT"
+    implementation "org.spigotmc:spigot-api:1.18-R0.1-SNAPSHOT"
     implementation "com.sk89q:squirrelid:0.2.0"
     implementation "net.milkbowl.vault:VaultAPI:1.7"
     implementation "org.anjocaido:essentialsgroupmanager:2.10.1"