Update dependency ruby to v2.5.3

Author: renovate[bot]

.circleci/config.yml

@@ -3,7 +3,7 @@ version: 2.1 # Set the CI version.
 # We use orbs to provide some common ruby and node tasks and shorten our config.
 # Learn more about orbs: https://circleci.com/orbs/
 orbs:
-  ruby: circleci/ruby@2.5.2
+  ruby: circleci/ruby@2.5.3
   node: circleci/node@7.1.0
   md-proofer: hubci/md-proofer@0.1.1
   vale: circleci/vale@1.2.0