chore: bump version to e5.0.2-rc.6

apps/emqx/include/emqx_release.hrl

@@ -35,7 +35,7 @@
 -define(EMQX_RELEASE_CE, "5.0.21").
 
 %% Enterprise edition
--define(EMQX_RELEASE_EE, "5.0.2-rc.5").
+-define(EMQX_RELEASE_EE, "5.0.2-rc.6").
 
 %% the HTTP API version
 -define(EMQX_API_VERSION, "5.0").