Not sure why I introduced this test at r28378, but it causes pasting to

Not sure why I introduced this test at r28378, but it causes pasting to
fail e.g., of URLs in math, since tocString() is called by
Paragraph::asString() to give us the contents of insets. Probably, I was
misled by the name, and the comment in Inset.h. That means, at least,
that this method is misnamed, but it probably means we do the wrong
thing in other cases.

git-svn-id: svn://svn.lyx.org/lyx/lyx-devel/trunk@36517 a592a061-630c-0410-9148-cb99ea01b6c8