Remove hack that avoided materialize in fallback broadcast

For reasons beyond my comprehensions, this previously failed to inline despite the at-inline. For reasons that are also beyond my comprehension, this hack is no longer necessary.

base/broadcast.jl

@@ -689,7 +689,7 @@ julia> string.(("one","two","three","four"), ": ", 1:4)
 
 ```
 """
-broadcast(f::Tf, As...) where {Tf} = copy(instantiate(broadcasted(f, As...)))
+broadcast(f::Tf, As...) where {Tf} = materialize(broadcasted(f, As...))
 
 # special cases defined for performance
 @inline broadcast(f, x::Number...) = f(x...)