Crypto Square: fix test case description (#2556)

* Crypto Square: fix test case description

54 character plaintext results in 8 chunks, not 7.

* new test reimplementing the old one

Author: keiravillekode

exercises/crypto-square/canonical-data.json

@@ -72,6 +72,16 @@
         "plaintext": "If man was meant to stay on the ground, god would have given us roots."
       },
       "expected": "imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn  sseoau "
+    },
+    {
+      "uuid": "33fd914e-fa44-445b-8f38-ff8fbc9fe6e6",
+      "reimplements": "fbcb0c6d-4c39-4a31-83f6-c473baa6af80",
+      "description": "54 character plaintext results in 8 chunks, the last two with trailing spaces",
+      "property": "ciphertext",
+      "input": {
+        "plaintext": "If man was meant to stay on the ground, god would have given us roots."
+      },
+      "expected": "imtgdvs fearwer mayoogo anouuio ntnnlvt wttddes aohghn  sseoau "
     }
   ]
 }