Add a lein tag to clojure image

...for completness with new boot tag

library/clojure

@@ -3,7 +3,7 @@ Maintainers: Paul Lam <[email protected]> (@Quantisan),
 GitRepo: https://github.com/Quantisan/docker-clojure.git
 GitCommit: f0fd68d6a197b4d1852aefab698b35ce1ea9881e
 
-Tags: lein-2.7.1, latest
+Tags: lein-2.7.1, lein, latest
 Directory: debian/lein
 
 Tags: lein-2.7.1-onbuild, onbuild