(CONT-949) - Bump stdlib dependency

Prior to this commit, postgresql module had allowed installations of
puppetlabs-stdlib versions < 5.2.0. This was incorrect as this module
references a type "Stdlib::IP::Address::V6::CIDR" that was released with
stdlib v5.2.0.

This commit bumps the dependency of puppetlabs/stdlib in metadata.json
to versions >= 5.2.0.

Author: jordanbreen28

metadata.json

@@ -10,7 +10,7 @@
   "dependencies": [
     {
       "name": "puppetlabs/stdlib",
-      "version_requirement": ">= 4.13.1 < 9.0.0"
+      "version_requirement": ">= 5.2.0 < 9.0.0"
     },
     {
       "name": "puppetlabs/apt",