Deques compilation error fix (#5591)

tests/collections/tdeques.nim

@@ -0,0 +1,17 @@
+discard """
+  output: '''true'''
+"""
+
+import deques
+
+
+proc index(self: Deque[int], idx: Natural): int =
+  self[idx]
+
+proc main =
+  var testDeque = initDeque[int]()
+  testDeque.addFirst(1)
+  assert testDeque.index(0) == 1
+
+main()
+echo "true"