Remove unused cassandra.yaml setting, max_value_size_in_mb, from 2.2.9

max_value_size_in_mb is currently in the 2.2.9 cassandra.yaml, but does not make reference of the config in any place within its codebase:

https://github.com/apache/cassandra/blob/cassandra-2.2.9/conf/cassandra.yaml#L888-L891

CASSANDRA-9530, which introduced max_value_size_in_mb, has it's Fix Version/s marked as 3.0.7, 3.7, and 3.8.

Let's remove the max_value_size_in_mb from the cassandra.yaml from >= 2.2.9, < 3.

~/repos/cassandra[(HEAD detached at cassandra-2.2.9)] (joaquin)$ grep -r max_value_size_in_mb .
conf/cassandra.yaml:# max_value_size_in_mb: 256