Docs: Update array-overlap.rst with some grammar improvements (#3997)
Docs: Update array-overlap.rst with some grammar improvements (#3997)

This PR updates the documentation section `Overlapping Computations` with some corrections to a few sentences in order to make them more clear and correct. 

Also, to make a few sentences easier to read, a few commas were added / removed.
ContinuumIO/dask,dask/dask,blaze/dask,jakirkham/dask,jcrist/dask,ContinuumIO/dask,blaze/dask,mrocklin/dask,mrocklin/dask,dask/dask,jcrist/dask,jakirkham/dask