fix: pom.xml to reduce vulnerabilities (#63)

The following vulnerabilities are fixed with an upgrade:
- https://snyk.io/vuln/SNYK-JAVA-ORGAPACHEHTTPCOMPONENTS-1016906

Author: snyk-bot

pom.xml

@@ -76,7 +76,7 @@
         <dependency>
             <groupId>org.apache.httpcomponents</groupId>
             <artifactId>httpclient</artifactId>
-            <version>4.5.12</version>
+            <version>4.5.13</version>
         </dependency>
 
         <!-- For parsing XML responses to POJOs -->