cql3/statements/create_index_statement: Remove static column validation
cql3/statements/create_index_statement: Remove static column validation

Apache Cassandra supports secondary indices on static columns since
commit 9e74891 ("Add support for secondary indexes on static columns").

duarten/scylla,scylladb/scylla,duarten/scylla,scylladb/scylla,scylladb/scylla,avikivity/scylla,duarten/scylla,avikivity/scylla,avikivity/scylla,scylladb/scylla