{Misc.} Fix up credscan false positive (#32847)

Author: a0x1ab

scripts/ci/credscan/CredScanSuppressions.json

@@ -683,6 +683,18 @@
         "src\\azure-cli\\azure\\cli\\command_modules\\network\\tests\\latest\\test_network_commands.py"
       ],
       "_justification": "[Network] False positive"
+    },
+    {
+      "placeholder": "asdfghjkl",
+      "_justification": "[ARO] Dummy client_secret value in test_validators.py unit tests"
+    },
+    {
+      "placeholder": "secret_123",
+      "_justification": "[ARO] Dummy client_secret value in test_validators.py unit tests"
+    },
+    {
+      "placeholder": "client_id_456",
+      "_justification": "[ARO] Dummy client_id value in test_validators.py unit tests"
     }
   ]
 }