Fix azure.IsNotFound for new azcore error type #1983

Job	Run time
comment-notification	0s
version / Calculate Dev Version	2s
build_test / Build binaries and schema	3m 52s
build_test / Test Provider	7m 58s
build_test / Build SDKs (nodejs)	9m 7s
build_test / Provider Dist	9m 3s
build_test / Build SDKs (python)	7m 27s
build_test / Build SDKs (dotnet)	14m 5s
build_test / Build SDKs (go)	16m 17s
build_test / Build SDKs (java)	4m 49s
build_test / Test pulumi/examples (nodejs)	2m 36s
build_test / Test SDKs (nodejs)	7m 58s
build_test / Test pulumi/examples (python)	2m 40s
build_test / Test pulumi/examples (dotnet)	2m 35s
build_test / Test SDKs (python)	8m 4s
build_test / Test pulumi/examples (go)	2m 49s
build_test / Test SDKs (dotnet)	11m 15s
build_test / Test pulumi/examples (java)	2m 24s
build_test / Test SDKs (go)	9m 1s
build_test / Test SDKs (java)	3m 8s
	2h 5m 10s

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