Task #544791: Replace SSH password authentication with SSH key authentication in tutorial-create-route-table.md

- Replaced --authentication-type password with --generate-ssh-keys for vm-nva (line 360)
- Replaced --authentication-type password with --generate-ssh-keys for vm-public (line 528)
- Replaced --authentication-type password with --generate-ssh-keys for vm-private (line 543)
- Aligns with Azure security best practices by using SSH key pairs instead of password authentication
- All three VMs in this tutorial now consistently use SSH key authentication

Author: asudbring

articles/virtual-network/tutorial-create-route-table.md

@@ -357,7 +357,7 @@ az vm create \
     --subnet subnet-dmz \
     --vnet-name vnet-1 \
     --admin-username azureuser \
-    --authentication-type password
+    --generate-ssh-keys
 ```
 
 The virtual machine takes a few minutes to create. Don't continue to the next step until Azure finishes creating the virtual machine and returns output for the virtual machine.
@@ -525,7 +525,7 @@ az vm create \
     --subnet subnet-1 \
     --public-ip-address "" \
     --admin-username azureuser \
-    --authentication-type password \
+    --generate-ssh-keys \
     --no-wait
 ```
 
@@ -540,7 +540,7 @@ az vm create \
     --subnet subnet-private \
     --public-ip-address "" \
     --admin-username azureuser \
-    --authentication-type password
+    --generate-ssh-keys
 ```
 ---