[Test] Bump password length to meet FIPS requirement (#74662)

Resolves: #74641

qa/system-indices/build.gradle

@@ -25,5 +25,5 @@ tasks.named("javaRestTest").configure {
 testClusters.all {
   testDistribution = 'DEFAULT'
   setting 'xpack.security.enabled', 'true'
-  user username: 'rest_user', password: 'password', role: 'superuser'
+  user username: 'rest_user', password: 'rest-user-password', role: 'superuser'
 }

qa/system-indices/src/javaRestTest/java/org/elasticsearch/system/indices/NetNewSystemIndicesIT.java

@@ -26,7 +26,7 @@ import static org.hamcrest.Matchers.not;
 
 public class NetNewSystemIndicesIT extends ESRestTestCase {
 
-    static final String BASIC_AUTH_VALUE = basicAuthHeaderValue("rest_user", new SecureString("password".toCharArray()));
+    static final String BASIC_AUTH_VALUE = basicAuthHeaderValue("rest_user", new SecureString("rest-user-password".toCharArray()));
 
     @Override
     protected Settings restClientSettings() {