Tests: Decrease log level for adding a header value (#28246)

This logging message adds considerable noise to many REST tests, if you
are using something like HTTP basic auth in every API call or set any custom
header.

The log level moves from info to debug, so can still be seen if wanted.

test/framework/src/main/java/org/elasticsearch/test/rest/yaml/ClientYamlTestClient.java

@@ -165,7 +165,7 @@ public class ClientYamlTestClient {
         Header[] requestHeaders = new Header[headers.size()];
         int index = 0;
         for (Map.Entry<String, String> header : headers.entrySet()) {
-            logger.info("Adding header {} with value {}", header.getKey(), header.getValue());
+            logger.debug("Adding header {} with value {}", header.getKey(), header.getValue());
             requestHeaders[index++] = new BasicHeader(header.getKey(), header.getValue());
         }