Update map_fp2_to_G2_bls.md

formats/map_fp2_to_G2_bls.md

@@ -11,7 +11,7 @@ The test data is declared in a 'json' file:
     {
         "Input": 128 bytes as an input that is interpreted as a an element of the quadratic extension field,
         "Name": the name of the test,
-        "Expected": single G1 point 128 bytes,
+        "Expected": single G2 point 256 bytes,
         "Gas": the cost of the gas,
         "NoBenchmark": True/False
     },