Docs - Fix formatting of Cassandra code block #987

Job	Run time
build-and-test / build-scala	4m 47s
build-and-test / accumulo-ds-tests / unit-tests	6m 42s
build-and-test / accumulo-other-tests / unit-tests	5m 7s
build-and-test / arrow-tests / unit-tests	26s
build-and-test / convert-tests / unit-tests	1m 50s
build-and-test / cqengine-tests / unit-tests	28s
build-and-test / cassandra-tests / unit-tests	1m 23s
build-and-test / features-tests / unit-tests	1m 40s
build-and-test / fs-tests / unit-tests	3m 49s
build-and-test / gt-tests / unit-tests	1m 13s
build-and-test / hbase-tests / unit-tests	2m 47s
build-and-test / lambda-tests / unit-tests	2m 30s
build-and-test / kafka-tests / unit-tests	2m 44s
build-and-test / metrics-tests / unit-tests	24s
build-and-test / integration-tests / integration-tests	4m 45s
build-and-test / other-tests / unit-tests	1m 5s
build-and-test / process-tests / unit-tests	24s
build-and-test / redis-tests / unit-tests	33s
build-and-test / spark-tests / unit-tests	1m 41s
build-and-test / utils-tests / unit-tests	37s
	44m 55s

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