crmMosaicoIframe - Fix height
crmMosaicoIframe - Fix height

The old height caused the bottom to appear cut-off by 25px.  This was
immediately obvious, but it would (eg) be difficult to see the last item in
the palette of blocks.

veda-consulting/uk.co.vedaconsulting.mosaico,veda-consulting/uk.co.vedaconsulting.mosaico,veda-consulting/uk.co.vedaconsulting.mosaico,veda-consulting/uk.co.vedaconsulting.mosaico