Update pt.json fix grammatical error (#48)

fix grammatical error in numbers 16, 17

Author: lucascdsilva

lib/i18n/pt.json

@@ -20,8 +20,8 @@
     "13": "treze",
     "14": "catorze",
     "15": "quinze",
-    "16": "dezasseis",
-    "17": "dezassete",
+    "16": "dezesseis",
+    "17": "dezessete",
     "18": "dezoito",
     "19": "dezenove",
     "20": "vinte",