i.vi: fix typo in ndvi from Sentinel bands

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@71554 15284696-431f-4ddb-bdfa-cd5b030d7da7

imagery/i.vi/i.vi.html

@@ -207,7 +207,7 @@ Satellite specific band numbers ([NIR, Red]):
   MSS Bands        = [ 7,  5]
   TM1-5,7 Bands    = [ 4,  3]
   TM8 Bands        = [ 5,  4]
-  Sentinel-2 Bands = [ 5,  4]
+  Sentinel-2 Bands = [ 8,  4]
   AVHRR Bands      = [ 2,  1]
   SPOT XS Bands    = [ 3,  2]
   AVIRIS Bands     = [51, 29]