Update VE core submodule to master (e76e259)

New changes:
f033911 Only run showSelection if one of the command successfully executed
381aee1 Remove ve.instances
df0f7e5 Rerender ContentBranchNodes when the selection anchor leaves
27d7517 Check the selection is in the correct surface
40101e4 Use a chimera instead of &#xFEFF; in inline slugs

Change-Id: I6af416ccc99c42e0595f0a52dbb348c710ea7e73