Fix (presumed) typo in container-instances-managed-identity.md

Every other instance of this string, in both JSON and YAML, is `SystemAssigned`, so I assume this instance should be `SystemAssigned` rather than `System Assigned` (with a space)?

(But since you're already parsing a comma-and-whitespace-separated string for this list of values, rather than just taking a JSON array, anything is possible)

Hopefully a useful drive-by typo improvement. I note that #113619 raises far more substantial issues with this page which still haven't been addressed.

Author: eddyashton

articles/container-instances/container-instances-managed-identity.md

@@ -327,7 +327,7 @@ On a container group, you can enable both a system-assigned identity and one or
 
 ```json
 "identity": {
-    "type": "System Assigned, UserAssigned",
+    "type": "SystemAssigned, UserAssigned",
     "userAssignedIdentities": {
         "myResourceID1": {
             }