Switch from shouty case to lowercase for header sanitization.

lib/requests.js

@@ -174,7 +174,7 @@ function _sanitizeHeaders({httpMessage, headers = sanitizeHeaders}) {
   for(const header of headers) {
     // sanitize the headers to prevent
     // authn tokens / information potentially in logs
-    newHeaders.set(header, '** SANITIZED TO PREVENT EXPOSING OF SECRETS ***');
+    newHeaders.set(header, 'sanitized');
   }
   return newHeaders;
 }