Update lasso selection description in core.yaml

[jidanni]

Sure, if the user could find

multiselect_lasso: "Another way to select multiple features is to hold down the {shift} key, then press and hold down the {leftclick} left mouse button and drag the mouse to draw a selection lasso. All of the points inside the lasso area will be selected.

via a mouseover while looking at the keyboards shortcut list, this change wouldn't be needed.

Else users will bang their head: why can't I select those houses?

(No, a subsequent CTRL+up arrow won't select the way that the nodes are from either. Only works when one node is selected.)