Update mixin targets renamed by Mojang in 26.2-snap-5

Fixes #2187

src/main/java/carpet/mixins/WorldGenRegion_scarpetPlopMixin.java

@@ -11,7 +11,7 @@ import org.spongepowered.asm.mixin.injection.callback.CallbackInfo;
 @Mixin(WorldGenRegion.class)
 public class WorldGenRegion_scarpetPlopMixin
 {
-    @Inject(method = "markPosForPostprocessing", at = @At("HEAD"), cancellable = true)
+    @Inject(method = "markPosForPostProcessing", at = @At("HEAD"), cancellable = true)
     private void markOrNot(BlockPos blockPos, CallbackInfo ci)
     {
         if (CarpetSettings.skipGenerationChecks.get()) ci.cancel();