Update adventure to v4.21.0

Author: renovate[bot]

gradle/libs.versions.toml

@@ -21,7 +21,7 @@ plotsquared = "7.5.2"
 bstats = "3.1.0"
 sparsebitset = "1.3"
 parallelgzip = "1.0.5"
-adventure = "4.20.0"
+adventure = "4.21.0"
 adventure-bukkit = "4.3.4"
 checkerqual = "3.49.3"
 truezip = "6.8.4"