Lower UnboundTestOperation to WARNING

Consumers of this package using the `includeServices` transform may not
also be running `removeUnusedShapes`, leaving behind operations that then
trip this validation and cause an error. Lowering this to a warning still
emits a message but doesn't block consumers until we find a better strategy
for running this validation at Smithy-only build time.

Author: kstich

smithy-aws-protocol-tests/model/shared-types.smithy

@@ -22,6 +22,7 @@ metadata validators = [
     {
         name: "EmitEachSelector"
         id: "UnboundTestOperation"
+        severity: "WARNING"
         message: "This operation in the AWS protocol tests is not bound to a service."
         namespaces: [
             // Overall protocol test suites.

smithy-protocol-tests/model/shared-types.smithy

@@ -11,6 +11,7 @@ metadata validators = [
     {
         name: "EmitEachSelector"
         id: "UnboundTestOperation"
+        severity: "WARNING"
         message: "This operation in the Smithy protocol tests is not bound to a service."
         namespaces: [
             // Overall protocol test suites.