Fix terrain not rendering with OF shaders enabled (fixes #122)

This was caused by us setting `needsTerrainUpdate` to false during the shadow
pass in order to break out of the ForceChunkLoading loop (cause OF doesn't
update chunks during the shadow pass). However, this inadvertently caused the
chunk updates to be skipped during the normal pass as well if there didn't
happen to be another reasons for updating.

To fix this, we simply move the shadow pass check into the ForceChunkLoading
mixin and skip the entire loop during the shadow pass.

src/main/resources/mixins.compat.shaders.replaymod.json

@@ -10,7 +10,6 @@
     //#if MC>=10800
     "MixinShaderEntityRenderer",
     "MixinShaderRenderChunk",
-    "MixinShaderRenderGlobal",
     //#else
     //$$ "MixinShaders",
     //#endif