chore(deps): update net.md-5:bungeecord-api to v1.21-R0.3

Author: renovate[bot]

gradle/libs.versions.toml

@@ -7,7 +7,7 @@ adventure = "4.17.0"
 adventure-platform = "4.3.3"
 
 # Platforms
-platform-bungeecord = "1.20-R0.3-SNAPSHOT"
+platform-bungeecord = "1.21-R0.3"
 
 # Dependencies
 updatelib = "4.0.0"