Unsuppress deprecated IoT operations (#6548)

* Unsuppress deprecated IoT operations

As customers move from V1 (which exposes these operations), to V2, they
may not be able to move to the recommended operations because of
external constraints such as IAM policies that only allow certain
operations.

Note: IoT is not the only service that has suppressed operations. We
will unsuppress them on need basis to avoid cluttering clients
unnecessarily.

* Add changelog

Author: dagnir

.changes/next-release/feature-AWSIoT-e90fa27.json

@@ -0,0 +1,6 @@
+{
+    "type": "feature",
+    "category": "AWS IoT",
+    "contributor": "",
+    "description": "Unsuppress the following operations that were previously suppressed:\n\n - AttachPrincipalPolicy\n - DetachPrincipalPolicy\n - ListPolicyPrincipals\n - ListPrincipalPolicies\n\nThese operations were previously supporessed because they were deprecated. However, this may be a blocker for customers moving from V1 to V2, so make these available for those customers."
+}

services/iot/src/main/resources/codegen-resources/customization.config

@@ -44,12 +44,6 @@
         "listAuditFindings",
         "listV2LoggingLevels"
     ],
-    "deprecatedOperations": [
-        "AttachPrincipalPolicy",
-        "DetachPrincipalPolicy",
-        "ListPolicyPrincipals",
-        "ListPrincipalPolicies"
-    ],
     "shapeModifiers": {
         "AssetPropertyVariant": {
             "union": true