Bump version for `count` deprecation.

Changelog.md

+# Changelog
+
+This changelog has a great deal of catch-up still to be done, but rather than further postponing its creation, we are just going to start here.
+
+| Version | Date             | Description                                             |
+|---------|------------------|---------------------------------------------------------|
+| 1.5.3   | [2021-05-23 Sun] | Deprecate the use of `count` as synonym for `counting`. |
+|         |                  |                                                         |

iterate.asd

@@ -3,7 +3,7 @@
 (defsystem :iterate
   :description "Jonathan Amsterdam's iterator/gatherer/accumulator facility"
   :licence "MIT"
-  :version "1.5.2"
+  :version "1.5.3"
   :in-order-to ((test-op (test-op :iterate/tests)))
   :components ((:file "package")
                (:file "iterate" :depends-on ("package"))))