Updated lower bound for the version requirement of org.eclipse.ui.ide.
This is required to see
org.eclipse.ui.internal.views.helpers.EmptyWorkspaceHelper added in
3.15.0 version of org.eclipse.ui.ide.

Change-Id: Iee45b6d15115d30328c106ff8dc811f4d7ee9d25
Signed-off-by: Andrey Loskutov <loskutov@gmx.de>