builtin: minor documentation improvements

std/builtin.jule

@@ -149,11 +149,11 @@ fn make(T, ...V): T
 //  If destination slice is []byte, source might be str also.
 fn copy(mut dest: Dest, mut src: Src): int
 
-// If there is enough capacity, it adds to the target slice.
+// If there is enough capacity, it adds to the destination slice.
 // If there is not enough capacity, it creates a copy of the
-// target slice with enough capacity and adds the new
+// destination slice with enough capacity and adds the new
 // elements and returns the new allocation.
-fn append(mut src: []T, mut items: ...T): []T
+fn append(mut dest: []T, mut items: ...T): []T
 
 // Returns length of T.
 //