Update VE core submodule to master (afbe6b5)

New changes:
1787e33 Fix ContentBranchNode echo suppression at the ends of text nodes
8e8a6be Refactor getToolsForNode and getToolsForAnnotation
f967be6 Localisation updates from https://translatewiki.net.
8f14d05 Prevent comparable annotations from being applied twice
f37887a Check if newly focused slug is different to previous slug
d13bb36 Localisation updates from https://translatewiki.net.
afbe6b5 Update OOjs UI to v0.1.0-pre (53f2410336)

Change-Id: I4836f8df2d2cafa313f54e127f2445f7d8cd445d