Update VE core submodule to master (6f1b98e)

New changes:
247ee74 Set size to default on 0 value
dd00977 ve.ce.CommentNode: Correct comments formatting
bafad68 Update OOjs UI to v0.1.0-pre (24ac83a472)
0b24cbc Localisation updates from https://translatewiki.net.
a6ca80a Followup cc657c4: make code and strikethrough key commands actually work

Change-Id: Ic0dad055bc7e725f23de947ff56a83e463239cc6