Docs: Update diagnostics-distributed.rst (#4277)
Docs: Update diagnostics-distributed.rst (#4277)

This PR updates `diagnostics-distributed.rst` with a couple punctuation improvements (minor things)
mrocklin/dask,blaze/dask,jcrist/dask,jakirkham/dask,dask/dask,dask/dask,jakirkham/dask,mrocklin/dask,ContinuumIO/dask,ContinuumIO/dask,jcrist/dask,blaze/dask