Removed unused numpy import in core/dimension.py
Removed unused numpy import in core/dimension.py

ioam/holoviews,mjabri/holoviews,basnijholt/holoviews,ioam/holoviews,mjabri/holoviews,basnijholt/holoviews,vascotenner/holoviews,ioam/holoviews,vascotenner/holoviews,mjabri/holoviews,vascotenner/holoviews,basnijholt/holoviews