DOC: Fix Array.cache examples
DOC: Fix Array.cache examples

dask/dask,ContinuumIO/dask,blaze/dask,jakirkham/dask,vikhyat/dask,mraspaud/dask,chrisbarber/dask,mikegraham/dask,jakirkham/dask,ContinuumIO/dask,jcrist/dask,blaze/dask,cowlicks/dask,mraspaud/dask,vikhyat/dask,mrocklin/dask,gameduell/dask,mrocklin/dask,jcrist/dask,cpcloud/dask,dask/dask