src/recon.app.src: Remove deprecated `maintainers` field

Hex.pm does not accept the `maintainers` field anymore and refuse to
publish if it exists.
diff --git a/src/recon.app.src b/src/recon.app.src
index 697b15f..c7cea40 100644
--- a/src/recon.app.src
+++ b/src/recon.app.src
@@ -5,7 +5,6 @@
   {registered, []},
   {applications, [kernel, stdlib]},
 
-  {maintainers, ["Fred Hebert"]},
   {licenses, ["BSD"]},
   {links, [{"Github", "https://github.com/ferd/recon/"},
            {"Documentation", "http://ferd.github.io/recon/"}]},