Fix Optifine detection

I really should have tested this. And not expected Optifine to be
normal.

src/main/java/dan200/computercraft/shared/integration/Optifine.java

@@ -0,0 +1,39 @@
+/*
+ * This file is part of ComputerCraft - http://www.computercraft.info
+ * Copyright Daniel Ratcliffe, 2011-2022. Do not distribute without permission.
+ * Send enquiries to dratcliffe@gmail.com
+ */
+package dan200.computercraft.shared.integration;
+
+/**
+ * Detect whether Optifine is installed.
+ */
+public final class Optifine
+{
+    private static final boolean LOADED;
+
+    static
+    {
+        boolean loaded;
+        try
+        {
+            Class.forName( "optifine.Installer", false, Optifine.class.getClassLoader() );
+            loaded = true;
+        }
+        catch( ReflectiveOperationException | LinkageError ignore )
+        {
+            loaded = false;
+        }
+
+        LOADED = loaded;
+    }
+
+    private Optifine()
+    {
+    }
+
+    public static boolean isLoaded()
+    {
+        return LOADED;
+    }
+}

src/main/java/dan200/computercraft/shared/peripheral/monitor/MonitorRenderer.java

@@ -7,7 +7,7 @@ package dan200.computercraft.shared.peripheral.monitor;
 
 import dan200.computercraft.ComputerCraft;
 import dan200.computercraft.client.render.TileEntityMonitorRenderer;
-import net.minecraftforge.fml.ModList;
+import dan200.computercraft.shared.integration.Optifine;
 import org.lwjgl.opengl.GL;
 
 import javax.annotation.Nonnull;
@@ -60,7 +60,7 @@ public enum MonitorRenderer
             return VBO;
         }
 
-        if( ModList.get().isLoaded( "optifine" ) )
+        if( Optifine.isLoaded() )
         {
             ComputerCraft.log.warn( "Optifine is loaded, assuming shaders are being used. Falling back to VBO monitor renderer." );
             return VBO;