fully qualify promote_eltypeof call (#411)

Missed in #407, but
causing doctest build to fail when we try to use this.

Author: vtjnash

src/sparsevector.jl

@@ -1236,7 +1236,7 @@ function hvcat(rows::Tuple{Vararg{Int}}, X::_SparseConcatGroup...)
     if anysparse(X...)
         vcat(_hvcat_rows(rows, X...)...)
     else
-        Base.typed_hvcat(promote_eltypeof(X...), rows, X...)
+        Base.typed_hvcat(Base.promote_eltypeof(X...), rows, X...)
     end
 end
 function _hvcat_rows((row1, rows...)::Tuple{Vararg{Int}}, X::_SparseConcatGroup...)