Bump puma from 4.3.8 to 4.3.9 in /examples/simple_rails_api (#117)

Author: dependabot[bot]

examples/simple_rails_api/Gemfile.lock

@@ -82,11 +82,11 @@ GEM
     mini_portile2 (2.5.3)
     minitest (5.14.4)
     msgpack (1.4.2)
-    nio4r (2.5.7)
+    nio4r (2.5.8)
     nokogiri (1.11.7)
       mini_portile2 (~> 2.5.0)
       racc (~> 1.4)
-    puma (4.3.8)
+    puma (4.3.9)
       nio4r (~> 2.0)
     racc (1.5.2)
     rack (2.2.3)