Bump mavenizer, fixes vanilla missing mc.version json entry

Author: LexManos

src/main/java/net/minecraftforge/gradle/internal/Tools.java

@@ -11,5 +11,5 @@ private Tools() { }
 
     static final Tool SLIMELAUNCHER = Tool.ofForge("slimelauncher", "net.minecraftforge:slime-launcher:0.2.1", 8, "net.minecraftforge.launcher.Main");
 
-    static final Tool MAVENIZER = Tool.ofForge("mavenizer", "net.minecraftforge:minecraft-mavenizer:0.5.10", 25, "net.minecraftforge.mcmaven.cli.Main");
+    static final Tool MAVENIZER = Tool.ofForge("mavenizer", "net.minecraftforge:minecraft-mavenizer:0.5.12", 25, "net.minecraftforge.mcmaven.cli.Main");
 }