dep: drop dependency on go-cmp in protocol tests (#2506)

Author: lucix-aws

.changelog/78a150058fc64beb866a236d2c44a071.json

@@ -0,0 +1,15 @@
+{
+    "id": "78a15005-8fc6-4beb-866a-236d2c44a071",
+    "type": "feature",
+    "collapse": true,
+    "description": "Drop dependency on go-cmp in protocol tests.",
+    "modules": [
+        "internal/protocoltest/awsrestjson",
+        "internal/protocoltest/ec2query",
+        "internal/protocoltest/jsonrpc",
+        "internal/protocoltest/jsonrpc10",
+        "internal/protocoltest/query",
+        "internal/protocoltest/restxml",
+        "internal/protocoltest/restxmlwithnamespace"
+    ]
+}