Flaky CQL test: updateConfigurationShouldRemoveGraphFromCache

## Flaky Test

* **Test Name:** CQLConfiguredGraphFactoryTest>AbstractConfiguredGraphFactoryTest.updateConfigurationShouldRemoveGraphFromCache
* **Link:** https://github.com/JanusGraph/janusgraph/blob/ba93c4bfda9e4c72b01aae7dc2ee9c3c5b5f37d1/janusgraph-backend-testutils/src/main/java/org/janusgraph/core/AbstractConfiguredGraphFactoryTest.java#L233
* **Branch:** `master`, PR was #3095
* **Notes:** The job was: `tests (cql, -Pcassandra3-murmur -Dtest="**/core/cql/*", murmur-core, 8)`. It passed on the second try.

### Stack Trace

```
Failures:
Error: CQLConfiguredGraphFactoryTest>AbstractConfiguredGraphFactoryTest.updateConfigurationShouldRemoveGraphFromCache:233 Expected java.lang.IllegalArgumentException to be thrown, but nothing was thrown.
```

Start with updateConfigurationShouldRemoveGraphFromCache in janusgraph-backend-testutils/src/main/java/org/janusgraph/core/AbstractConfiguredGraphFactoryTest.java at line 233. Run the reported CQL test command with the Cassandra 3 Murmur profile and inspect why the test sometimes does not throw IllegalArgumentException. Done means the test reliably enforces the expected exception without flaking.

Written by the indexing model from the issue text.