chore(emqx_exhook): Delete old app.src file

apps/emqx_exhook/src/emqx_extension_hook.app.src

@@ -1,14 +0,0 @@
-{application, emqx_extension_hook,
- [{description, "EMQ X Extension for Hook"},
-  {vsn, "git"},
-  {modules, []},
-  {registered, []},
-  {mod, {emqx_extension_hook_app, []}},
-  {applications, [kernel, stdlib, ecpool, erlport]},
-  {env,[]},
-  {licenses, ["Apache-2.0"]},
-  {maintainers, ["EMQ X Team <contact@emqx.io>"]},
-  {links, [{"Homepage", "https://emqx.io/"},
-           {"Github", "https://github.com/emqx/emqx-extension-hook"}
-          ]}
- ]}.