fix: defender management group name (#201)

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## Overview/Summary

Match the updated management group id

## This PR fixes/adds/changes/removes

None

### Breaking Changes

None

## Testing Evidence

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works/fixes as described and planned (include screenshots, if
appropriate).

## As part of this Pull Request I have

- [x] Checked for duplicate [Pull
Requests](https://github.com/Azure/alz-terraform-accelerator/pulls)
- [x] Associated it with relevant
[issues](https://github.com/Azure/alz-terraform-accelerator/issues), for
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- [x] Ensured my code/branch is up-to-date with the latest changes in
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templates/platform_landing_zone/examples/full-multi-region-nva/hub-and-spoke-vnet.tfvars

@@ -199,7 +199,7 @@ management_group_settings = {
     }
   }
   policy_assignments_to_modify = {
-    alzroot = {
+    alz = {
       policy_assignments = {
         Deploy-MDFC-Config-H224 = {
           parameters = {

templates/platform_landing_zone/examples/full-multi-region-nva/virtual-wan.tfvars

@@ -193,7 +193,7 @@ management_group_settings = {
     }
   }
   policy_assignments_to_modify = {
-    alzroot = {
+    alz = {
       policy_assignments = {
         Deploy-MDFC-Config-H224 = {
           parameters = {

templates/platform_landing_zone/examples/full-multi-region/hub-and-spoke-vnet.tfvars

@@ -201,7 +201,7 @@ management_group_settings = {
     }
   }
   policy_assignments_to_modify = {
-    alzroot = {
+    alz = {
       policy_assignments = {
         Deploy-MDFC-Config-H224 = {
           parameters = {

templates/platform_landing_zone/examples/full-multi-region/virtual-wan.tfvars

@@ -190,7 +190,7 @@ management_group_settings = {
     }
   }
   policy_assignments_to_modify = {
-    alzroot = {
+    alz = {
       policy_assignments = {
         Deploy-MDFC-Config-H224 = {
           parameters = {

templates/platform_landing_zone/examples/full-single-region/hub-and-spoke-vnet.tfvars

@@ -173,7 +173,7 @@ management_group_settings = {
     }
   }
   policy_assignments_to_modify = {
-    alzroot = {
+    alz = {
       policy_assignments = {
         Deploy-MDFC-Config-H224 = {
           parameters = {

templates/platform_landing_zone/examples/full-single-region/virtual-wan.tfvars

@@ -168,7 +168,7 @@ management_group_settings = {
     }
   }
   policy_assignments_to_modify = {
-    alzroot = {
+    alz = {
       policy_assignments = {
         Deploy-MDFC-Config-H224 = {
           parameters = {

templates/platform_landing_zone/examples/management-only/management.tfvars

@@ -136,7 +136,7 @@ management_group_settings = {
     }
   }
   policy_assignments_to_modify = {
-    alzroot = {
+    alz = {
       policy_assignments = {
         Deploy-MDFC-Config-H224 = {
           parameters = {