Revert "version up: re6stnet 0.573"

This reverts commit 0c629b21.

This was not the way of upgrading the package in chrombrew build.

buildout.cfg

@@ -37,9 +37,7 @@ configure-options +=
   --with-libiconv=gnu
 
 [versions]
+re6stnet = 0.551
 miniupnpc = 2.0.2
 maxminddb = 1.4.1
 geoip2 = 2.9.0
-
-[re6stnet-repository]
-revision = f1e956608a42eac5fd64b8d7fe5bb0bdc9065190