[Postgres]: `?` JSON operator cannot be parsed without a space after the field name

When using `PostgreSqlDialect`, the question mark cannot be parsed if it is not followed by a space, whereas postgres accepts the query. The following code panics when parsing `broken`:

```rust
fn main() {
let broken = r#"SELECT user?'adress' FROM my_table"#;
let working = r#"SELECT user? 'adress' FROM my_table"#;

let working_parsed =
sqlparser::parser::Parser::parse_sql(&sqlparser::dialect::PostgreSqlDialect {}, working)
.expect("Failed to parse SQL query");
println!("{:?}", working_parsed);

let broken_parsed =
sqlparser::parser::Parser::parse_sql(&sqlparser::dialect::PostgreSqlDialect {}, broken)
.expect("Failed to parse SQL query");
println!("{:?}", broken_parsed);
}
```

首先运行随附的 Parser::parse_sql 示例并使用 PostgreSqlDialect，比较两种查询形式。跟踪解析器如何处理字段名旁边的 ?，然后为两种空格形式添加覆盖，并确认 PostgreSQL JSON 运算符解析时不会 panic。

由索引模型根据 Issue 内容生成。