NDVI formula change in documentation

docs/source/product_user_guide/Indices.rst

@@ -8,7 +8,7 @@ Here are the radiometric indices available for computing in Sen2Chain. Indices c
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-    * - $$NDVI = {{NIR-VIR}\over{NIR+VIR}}$$
+    * - $$NDVI = {{NIR-RED}\over{NIR+RED}}$$
     * - $$NDWI(McFeeters) = {{GREEN-NIR}\over{GREEN+NIR}}$$
     * - $$NDWI(Gao) = {{NIR-SWIR}\over{NIR+SWIR}}$$
     * - $$MNDWI = {{GREEN-SWIR}\over{GREEN+SWIR}}$$