Update docs/_docs/internals/specialized-traits.md

Co-authored-by: Jamie Thompson <[email protected]>

Author: odersky

docs/_docs/internals/specialized-traits.md

@@ -16,7 +16,7 @@ As a first example, consider a `Vec` trait for vectors over a numeric type.
 ```scala
 import scala.math.Numeric
 
-inline trait Vec[T: {Specialized, Numeric}](elems: Array[T]):
+inline trait Vec[T: {Specialized, Numeric as num}](elems: Array[T]):
 
   def length = elems.length