Exclude two change stream tests from running inside the `sharding_csrs_continuous_config_stepdown` test suite.

This is required because the config stepdown suite will arbitrarily step down the config server, which can lead to the resharding change stream notification being sent multiple times. This can lead to unexpected/repeated resharding change events being emitted, which the two tests do not expect.

The change streams "ignore-removed-shards" smoke tests were already excluded from running in the config stepdown test suite, but the two files added here were missing.

This should fix the spurious test failures reported in BF-44452.