Replace "Add" with "Create" in description of Helper (#131407)

The user can create Statistics helpers for different purposes.

Following the HA Design guidelines this means that the description in the dialog should use "Create" not "Add".

homeassistant/components/statistics/strings.json

@@ -10,7 +10,7 @@
     },
     "step": {
       "user": {
-        "description": "Add a statistics sensor",
+        "description": "Create a statistics sensor",
         "data": {
           "name": "[%key:common::config_flow::data::name%]",
           "entity_id": "Entity"