[resourcemanager] The link for samples of rehydration has no such samples

[ArcturusZhang]

See: https://github.com/Azure/azure-sdk-for-net/blob/97a2911b0ff82385ee3499e2bb13c24b37f4d74f/sdk/resourcemanager/Azure.ResourceManager/README.md#rehydrate-a-long-running-operation
There is a link implying that there are more samples for this topic, but actually that directory does not have such samples

[ArcturusZhang]

it turns out the sentence is about "we have more examples in general", not just for redydration.
Therefore we move up that sentence to reduce the confusion.