Drop Ruby 3.0 support #216

Job	Run time
RBS	10s
RBS	10s
RuboCop	9s
RuboCop	9s
Linux, Cassandra 3, Ruby 3.1	1m 55s
Linux, Cassandra 3, Ruby 3.1	1m 44s
macOS, Ruby 3.1	1m 12s
macOS, Ruby 3.1	1m 12s
Linux, Cassandra 4, Ruby 3.1	1m 43s
Linux, Cassandra 4, Ruby 3.1	1m 43s
macOS, Ruby 3.2	1m 38s
macOS, Ruby 3.2	1m 38s
Linux, Cassandra 5, Ruby 3.1	1m 58s
Linux, Cassandra 5, Ruby 3.1	1m 58s
macOS, Ruby 3.3	1m 30s
macOS, Ruby 3.3	1m 30s
Linux, Cassandra 3, Ruby 3.2	1m 47s
Linux, Cassandra 3, Ruby 3.2	1m 47s
macOS, Ruby 3.4.0-preview1	1m 14s
macOS, Ruby 3.4.0-preview1	1m 14s
Linux, Cassandra 4, Ruby 3.2	1m 49s
Linux, Cassandra 4, Ruby 3.2	1m 49s
Linux, Cassandra 5, Ruby 3.2	1m 47s
Linux, Cassandra 5, Ruby 3.2	1m 47s
Linux, Cassandra 3, Ruby 3.3	1m 52s
Linux, Cassandra 3, Ruby 3.3	1m 52s
Linux, Cassandra 4, Ruby 3.3	1m 53s
Linux, Cassandra 4, Ruby 3.3	1m 53s
Linux, Cassandra 5, Ruby 3.3	1m 41s
Linux, Cassandra 5, Ruby 3.3	1m 41s
Linux, Cassandra 3, Ruby 3.4.0-preview1	1m 47s
Linux, Cassandra 3, Ruby 3.4.0-preview1	1m 47s
Linux, Cassandra 4, Ruby 3.4.0-preview1	1m 46s
Linux, Cassandra 4, Ruby 3.4.0-preview1	1m 46s
Linux, Cassandra 5, Ruby 3.4.0-preview1	1m 46s
Linux, Cassandra 5, Ruby 3.4.0-preview1	1m 46s
	55m 3s

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