Fix unparse table scan with the projection pushdown

[goldmedal]

Which issue does this PR close?

no corresponding issue.

Rationale for this change

The projection indices of a TableScan are the index number of its source schema. I used the projected_schema that is the output schema of the table scan in the previous PR. Some cases like the following one will fail because the index is out of the bound.

    let schema = Schema::new(vec![
        Field::new("id", DataType::Utf8, false),
        Field::new("age", DataType::Utf8, false),
    ]);

    let scan_with_projection = table_scan(Some("t1"), &schema, Some(vec![1]))?.build()?;
    let scan_with_projection = plan_to_sql(&scan_with_projection)?;
    assert_eq!(format!("{}", scan_with_projection), "SELECT t1.age FROM t1");

What changes are included in this PR?

• Use the source schema instead of projected_schema.

Are these changes tested?

yes

Are there any user-facing changes?

no

[alamb]

FYI @phillipleblanc and @sgrebnov , do you possibly have time to review this PR?

[sgrebnov]

@goldmedal , @alamb - the change looks good, thank you!

[phillipleblanc]

Thanks for catching and fixing this.

[alamb]

Thank you @goldmedal and for the reviews @phillipleblanc and @sgrebnov 🚀

We can keep the code moving fast with distributed review 🚋

[goldmedal]

Thanks @alamb @sgrebnov @phillipleblanc for the review 👍