fix(sqlglot30): handle bare LIMIT clause in get_limit_from_sql

sqlglot 30 raises ParseError for "SELECT ... LIMIT" (no value)
because Limit.expression is now a required keyword. Catch
SupersetParseError in get_limit_from_sql and return None, matching
the expected behavior for malformed LIMIT clauses.

Fixes test_extract_limit_from_query on postgres/mysql/sqlite.

Co-Authored-By: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>