Improve the "Swagger LintDiff"

Follow up on this [discussion](https://teams.microsoft.com/l/message/19:906c1efbbec54dc8949ac736633e6bdf@thread.skype/1747404934762?tenantId=72f988bf-86f1-41af-91ab-2d7cd011db47&groupId=3e17dcb0-4257-4a30-b843-77f47f1d4121&parentMessageId=1747404934762&teamName=Azure%20SDK&channelName=TypeSpec%20Discussion&createdTime=1747404934762), this pipeline fails many times for the TypeSpec migration PR. However, [the place I'm violating the rules, its swagger is the same as before](https://teams.microsoft.com/l/message/19:906c1efbbec54dc8949ac736633e6bdf@thread.skype/1747730687259?tenantId=72f988bf-86f1-41af-91ab-2d7cd011db47&groupId=3e17dcb0-4257-4a30-b843-77f47f1d4121&parentMessageId=1747404934762&teamName=Azure%20SDK&channelName=TypeSpec%20Discussion&createdTime=1747730687259). Therefore, we shouldn't report failure to give customers such noises. We should figure out a way to give customers clear signal if they are violating anything.

/cc @mikeharder @weshaggard @danieljurek