Increase limit on stdout, stderr in docker tests

json logs used in docker tests are consuming more space
than the previous 200KB
setting the limit to 2MB
relates elastic#99508

qa/os/src/test/java/org/elasticsearch/packaging/util/Shell.java

@@ -202,7 +202,7 @@ private Result runScriptIgnoreExitCode(String[] command) {
     private String readFileIfExists(Path path) throws IOException {
         if (Files.exists(path)) {
             long size = Files.size(path);
-            final int maxFileSize = 100 * 1024;
+            final int maxFileSize = 1024 * 1024;
             if (size > maxFileSize) {
                 // file is really big, truncate
                 try (var br = Files.newBufferedReader(path, StandardCharsets.UTF_8)) {