Adapt rabbit.snippets to new config format

Author: LoisSotoLopez

deps/rabbit/test/config_schema_SUITE_data/rabbit.snippets

@@ -1100,7 +1100,9 @@ credential_validator.regexp = ^abc\\d+",
   {message_interceptors,
    "message_interceptors.incoming.set_header_timestamp.overwrite = true",
    [{rabbit, [
-      {incoming_message_interceptors, [{set_header_timestamp, true}]}
+      {incoming_message_interceptors, [
+        {set_header_timestamp, #{overwrite => true}}
+       ]}
      ]}],
    []},
 
@@ -1110,8 +1112,10 @@ credential_validator.regexp = ^abc\\d+",
    message_interceptors.incoming.set_header_timestamp.overwrite = false
   ",
    [{rabbit, [
-      {incoming_message_interceptors, [{set_header_routing_node, false},
-                                       {set_header_timestamp, false}]}
+      {incoming_message_interceptors, [
+        {set_header_routing_node, #{overwrite => false}},
+        {set_header_timestamp, #{overwrite => false}
+       ]}
      ]}],
    []},