anagram: rm all "string argument" cases

the ant -> stand, tan, at case is exactly a duplicate of a case in the
"cases" section. The ant -> tan case is not a duplicate, but it does not
seem to provide any extra value as the description of the test "accepts
single string argument" is covered by, for example, galea -> eagle.

anagram.json

@@ -118,19 +118,5 @@
             "candidates": ["Banana"],
             "expected": []
         }
-    ],
-    "string argument cases": [
-        {
-            "description": "accepts string arguments",
-            "subject": "ant",
-            "candidates": ["stand", "tan", "at"],
-            "expected": ["tan"]
-        },
-        {
-            "description": "accepts single string argument",
-            "subject": "ant",
-            "candidates": ["tan"],
-            "expected": ["tan"]
-        }
     ]
 }