Memory leak in global distance field when bDisableWorldRendering=true

A memory leak occurs in global distance fields when bDisableWorldRendering=true

As a workaround until this is fixed, you can disable the logic that checks bUpdatedThisFrame *in *GlobalDistanceField.cpp locally.

1. DF AO must be enabled and used
2. set bDisableWorldRendering to false -> as a result FScene::IncrementFrameNumber() is not called and FrameNumber is not incremented
3. keep updating/moving stuff in background -> DistanceFieldSceneData.PrimitiveModifiedBounds is not empty
4. Render in scene capture -> ComputeUpdateRegionsAndUpdateViewState() is called. In it

ClipmapViewState.Cache[CacheType].PrimitiveModifiedBounds.Append(Scene->DistanceFieldSceneData.PrimitiveModifiedBounds[SourceCacheType]);

is called every frame, but PrimitiveModifiedBounds is never emptied, because *bUpdatedThisFrame *is true, because FrameNumber is never incremented.

Note: appending to PrimitiveModifiedBounds takes longer and longer every frame, since it's never emptied, so low FPS can be observed too. Eventually, memory is exhausted.