build!: update forge

Refer to:
- Issue #44: Forge mod loader may need to be updated
- Issue #37: Task list for version 2.0.0

Compatibility info:
- BREAKING CHANGES MAY RESULT from this commit.

mmc-pack.json

@@ -30,9 +30,9 @@
                     "uid": "net.minecraft"
                 }
             ],
-            "cachedVersion": "40.1.70",
+            "cachedVersion": "40.1.86",
             "uid": "net.minecraftforge",
-            "version": "40.1.70"
+            "version": "40.1.86"
         }
     ],
     "formatVersion": 1