Update VE core submodule to master (b6423de)

New changes:
3672954 Follow-up Ifa89a85e: Use '0' not '0px'
0cc0830 Normalize split text nodes correctly
c921dab Localisation updates from https://translatewiki.net.
3d1029b Trim whitespace when annotating

Change-Id: Ia5837dfb93b4eef76c32415462222bcfcfa6df3a