SinglyLinkedList.remove docs: Assumes -> asserts

Removing a node that is not in the list invokes safety-checked illegal behavior, so "asserts" is the recommended language to use.

lib/std/SinglyLinkedList.zig

@@ -86,7 +86,7 @@ pub fn prepend(list: *SinglyLinkedList, new_node: *Node) void {
 }
 
 /// Remove `node` from the list.
-/// Assumes `node` is in the list.
+/// Asserts that `node` is in the list.
 pub fn remove(list: *SinglyLinkedList, node: *Node) void {
     if (list.first == node) {
         list.first = node.next;