update template moving maintainers into extras field

priv/templates/otp_app.app.src

@@ -11,7 +11,6 @@
   {env,[]},
   {modules, []},
 
-  {maintainers, []},
   {licenses, ["Apache 2.0"]},
   {links, []}
  ]}.

priv/templates/otp_lib.app.src

@@ -9,7 +9,6 @@
   {env,[]},
   {modules, []},
 
-  {maintainers, []},
   {licenses, ["Apache 2.0"]},
   {links, []}
  ]}.