test: remove duplicated descriptions from tests

src/ahriman/core/configuration/configuration_multi_dict.py

@@ -54,10 +54,10 @@ class ConfigurationMultiDict(dict[str, Any]):
             value(Any): value of the related key
 
         Raises:
-            OptionError: if the key already exists in the dictionary, but not a single value list or a string
+            OptionError: if the key already exists in the dictionary, but not a single value list
         """
         match self.get(key):
-            case [current_value] | str(current_value):  # type: ignore[misc]
+            case [current_value]:
                 value = f"{current_value} {value}"
             case None:
                 pass

tests/ahriman/core/configuration/test_configuration_multi_dict.py

@@ -40,9 +40,9 @@ def test_setitem_array_exception() -> None:
     must raise exception if the current value is not a single value array
     """
     instance = ConfigurationMultiDict()
-    instance["key[]"] = ["value1", "value2"]
+    instance["key[]"] = "value1"
     with pytest.raises(OptionError):
-        instance["key[]"] = ["value3"]
+        instance["key[]"] = ["value2"]
 
 
 def test_setitem_exception() -> None: