suggestion_list: fix transposition cost

Replicates graphql/graphql-js@02cd678

Author: Cito

src/graphql/pyutils/suggestion_list.py

@@ -70,6 +70,6 @@ def measure(self, option: str):
                 d[i][j] = min(d[i - 1][j] + 1, d[i][j - 1] + 1, d[i - 1][j - 1] + cost)
 
                 if i > 1 and j > 1 and a[i - 1] == b[j - 2] and a[i - 2] == b[j - 1]:
-                    d[i][j] = min(d[i][j], d[i - 2][j - 2] + cost)
+                    d[i][j] = min(d[i][j], d[i - 2][j - 2] + 1)
 
         return d[a_len][b_len]