chore: bump `emqx_retainer` to 5.0.16

apps/emqx_retainer/src/emqx_retainer.app.src

@@ -2,7 +2,7 @@
 {application, emqx_retainer, [
     {description, "EMQX Retainer"},
     % strict semver, bump manually!
-    {vsn, "5.0.15"},
+    {vsn, "5.0.16"},
     {modules, []},
     {registered, [emqx_retainer_sup]},
     {applications, [kernel, stdlib, emqx, emqx_ctl]},