[chore][exporter/elasticsearch] Fix TestExporter_PushEvent flaky test (…

…open-telemetry#32917)

**Description:** <Describe what has changed.>
<!--Ex. Fixing a bug - Describe the bug and how this fixes the issue.
Ex. Adding a feature - Explain what this achieves.-->
Fix a flaky test from open-telemetry#31694 due to non-deterministic JSON key order.

**Link to tracking Issue:** Closes open-telemetry#32910

exporter/elasticsearchexporter/logs_exporter_test.go

@@ -173,9 +173,15 @@ func TestExporter_PushEvent(t *testing.T) {
 		server := newESTestServer(t, func(docs []itemRequest) ([]itemResponse, error) {
 			rec.Record(docs)
 
-			expected := `{"attrKey1":"abc","attrKey2":"def","application":"myapp","service":{"name":"myservice"},"error":{"stacktrace":"no no no no"},"agent":{"name":"otlp"},"@timestamp":"1970-01-01T00:00:00.000000000Z","message":"hello world"}`
-			actual := string(docs[0].Document)
-			assert.Equal(t, expected, actual)
+			var expectedDoc, actualDoc map[string]any
+			expected := []byte(`{"attrKey1":"abc","attrKey2":"def","application":"myapp","service":{"name":"myservice"},"error":{"stacktrace":"no no no no"},"agent":{"name":"otlp"},"@timestamp":"1970-01-01T00:00:00.000000000Z","message":"hello world"}`)
+			err := json.Unmarshal(expected, &expectedDoc)
+			require.NoError(t, err)
+
+			actual := docs[0].Document
+			err = json.Unmarshal(actual, &actualDoc)
+			require.NoError(t, err)
+			assert.Equal(t, expectedDoc, actualDoc)
 
 			return itemsAllOK(docs)
 		})