Fix incorrect SqlNodeVisitor parameter names for IS NULL predicates

[kaklakariada]

Problem

SqlNodeVisitor declares the visitor methods for SqlPredicateIsNotNull and SqlPredicateIsNull with the wrong parameter name and matching wrong Javadoc. Both methods currently use sqlPredicateOr, which appears to have been copied from the preceding SqlPredicateOr method.

public R visit(SqlPredicateIsNotNull sqlPredicateOr) throws AdapterException;
public R visit(SqlPredicateIsNull sqlPredicateOr) throws AdapterException;

Evidence

• src/main/java/com/exasol/adapter/sql/SqlNodeVisitor.java: the visit(SqlPredicateIsNotNull ...) and visit(SqlPredicateIsNull ...) method parameters and @param tags say sqlPredicateOr.
• src/main/java/com/exasol/adapter/request/renderer/PushdownSqlRenderer.java: the overriding implementations already use the clearer names sqlPredicateIsNotNull and sqlPredicateIsNull.

Why this matters

This is a public interface and the current names make generated documentation and IDE/search/refactoring workflows misleading. The API contract should identify the actual node type being visited.

Suggested fix

Rename the interface parameters and Javadoc tags to:

• sqlPredicateIsNotNull for visit(SqlPredicateIsNotNull ...)
• sqlPredicateIsNull for visit(SqlPredicateIsNull ...)