fix: use 1.21.6-Snapshot curseforge tag instead of 1.21.6 since it doesn't exist yet.

Author: isXander

versions/1.21.6-fabric/gradle.properties

@@ -8,4 +8,5 @@ deps.fabricApi=0.127.0+1.21.6
 
 meta.mcDep=~1.21.6
 
-pub.stableMC=1.21.6
+pub.modrinthMC=1.21.6
+pub.curseMC=1.21.6-Snapshot

versions/1.21.6-neoforge/gradle.properties

@@ -10,4 +10,5 @@ deps.kotlinForForge=5.6.0
 meta.mcDep=[1.21.6,1.22)
 meta.loaderDep=[21.6,22)
 
-pub.stableMC=1.21.6
+pub.modrinthMC=1.21.6
+pub.curseMC=1.21.6-Snapshot