chore(deps): Update dependency net.md-5:bungeecord-api to v1.21-R0.4

Author: renovate[bot]

gradle/libs.versions.toml

@@ -14,7 +14,7 @@ immutables = "2.11.4"
 brigadier = "1.0.18"
 bukkit = "1.13.2-R0.1-SNAPSHOT"
 commodore = "2.2"
-bungeecord = "1.20-R0.2"
+bungeecord = "1.21-R0.4"
 cloudburst = "1.0.0-SNAPSHOT"
 adventureApi = "4.15.0"
 adventurePlatform = "4.4.1"