[conv.general] Remove duplicate cross-reference to [dcl.init]

[Eisenwave]

The previous paragraph already contains the same \iref{dcl.init}, and normally, we don't duplicate these.

I'm also not sure whether this \iref is all that good in general, but I don't see any obvious improvement.

[jensmaurer]

I'd like to keep the cross-reference here, although it might look duplicate, because it's a "normative" pointer to the interpretation of the initialization syntax. The syntax is different in the preceding paragraph, and it's not necessarily clear that both syntaxes are covered by the same subclause.