Update -NAN to NAN

Author: raulcd

cpp/src/arrow/acero/hash_aggregate_test.cc

@@ -1579,7 +1579,7 @@ TEST_P(GroupBy, VarianceOptionsAndSkewOptions) {
                                R"([
          [1, null,      0.707106,  null,     null,    null,      -1.5,      null,      null    ],
          [2, 0.213833,  0.213833,  0.213833, 0.37037, -1.720164, -1.720164, -1.720164, -3.90123],
-         [3, 0.0,       null,      null,     -NaN,    -2.0,       null,     null,      -NaN    ],
+         [3, 0.0,       null,      null,     NaN,     -2.0,       null,     null,      NaN     ],
          [4, null,      0.707106,  null,     null,    null,      -1.5,      null,      null    ]
          ])");
       ValidateOutput(actual);

cpp/src/arrow/compute/kernels/aggregate_test.cc

@@ -3694,7 +3694,7 @@ TEST_F(TestSkewKurtosis, Options) {
     AssertSkewKurtosisAre(type, "[0, 1, null, 2]", options, 0.0, -1.5);
     AssertSkewKurtosisAre(type, {"[0, 1]", "[]", "[null, 2]"}, options, 0.0, -1.5);
     options.bias = false;
-    AssertSkewKurtosisAre(type, {"[0, 1]", "[]", "[null, 2]"}, options, 0.0, -NAN);
+    AssertSkewKurtosisAre(type, {"[0, 1]", "[]", "[null, 2]"}, options, 0.0, NAN);
     AssertSkewKurtosisAre(type, {"[1, 2, 3]", "[40, null]"}, options, 1.9889477403978211,
                           3.9631931024230695);
     options.bias = true;