Resetting local schema can cause assertion error

When a user resets their local schema the Schema class purges all CFmetadata and recreates it. If a compaction is going on this can cause an issue similar to CASSANDRA-8332

The original intent of the assertion was to ensure if the setLiveMetadata was never called with different metadata instances since the schema is managed as a global reference. However I missed this reset method so it's probably just as well to remove this assert.