Revert "Test for double attribute issue in ADIOS2 v2.7.1"

This reverts commit a39b618.

The test is added in PR #1302 which fixes the bug

Author: franzpoeschel

test/SerialIOTest.cpp

@@ -16,7 +16,6 @@
 
 #include <algorithm>
 #include <array>
-#include <chrono>
 #include <cmath>
 #include <complex>
 #include <fstream>
@@ -28,7 +27,6 @@
 #include <sstream>
 #include <stdexcept>
 #include <string>
-#include <thread>
 #include <tuple>
 #include <vector>
 
@@ -5834,13 +5832,6 @@ void append_mode(
         write.flush();
     }
     {
-        using namespace std::chrono_literals;
-        /*
-         * Put a little sleep here to trigger writing of a different /date
-         * attribute. ADIOS2 v2.7 does not like that so this test ensures that
-         * we deal with it.
-         */
-        std::this_thread::sleep_for(1s);
         Series write(filename, Access::APPEND, jsonConfig);
         if (variableBased)
         {