stack/slapos.cfg: version up rubygemsrecipe to 0.4.2

- rubygemsrecipe deployment mode now depends on `allow-picked-versions` by default

software/fluentd/software.cfg

@@ -23,4 +23,4 @@ context =
 [fluentd]
 gems +=
   fluent-plugin-wendelin==0.4
-  fluent-plugin-bin
+  fluent-plugin-bin==0.2

stack/slapos.cfg

@@ -188,7 +188,7 @@ requests = 2.24.0
 scandir = 1.10.0
 setproctitle = 1.1.10
 setuptools-dso = 1.7
-rubygemsrecipe  = 0.3.0
+rubygemsrecipe  = 0.4.2
 six = 1.12.0
 slapos.cookbook = 1.0.197
 slapos.core = 1.6.18