Use plus-minus symbol in model card

README.md

@@ -28,11 +28,11 @@ and the ceiling of non-convolutional models on MNIST.
 
 | metric | result |
 | --- | ---: |
-| validation accuracy | 99.3600% +/- 0.0817 pp |
-| validation loss | 0.15172 +/- 0.00235 |
-| test accuracy | 99.4470% +/- 0.0195 pp |
-| test loss | 0.14746 +/- 0.00034 |
-| test errors | 55.3 +/- 1.95 / 10000 |
+| validation accuracy | 99.3600% ± 0.0817 pp |
+| validation loss | 0.15172 ± 0.00235 |
+| test accuracy | 99.4470% ± 0.0195 pp |
+| test loss | 0.14746 ± 0.00034 |
+| test errors | 55.3 ± 1.95 / 10000 |
 
 ## Architecture