chore: bump httpclient5 version to 5.6

PiperOrigin-RevId: 875748670

Author: tilgalas

pom.xml

@@ -68,7 +68,7 @@
     <assertj.version>3.27.7</assertj.version>
     <anthropic.version>1.4.0</anthropic.version>
     <maven-plugin-tools.version>3.9.0</maven-plugin-tools.version>
-    <httpclient5.version>5.4.3</httpclient5.version>
+    <httpclient5.version>5.6</httpclient5.version>
   </properties>
 
   <dependencyManagement>