`TextPoolGenerator` is unused

[scsmithr]

Describe the issue

It's there, but nothing is using it. It is public, but I don't know when you would use it.

Could probably be deleted.

[kevinjqliu]

Seems safe to remove.

TextPoolGenerator was first introduced here then removed a few commits later here, in the tpchgen/src/textgen.rs file.

It was then re-added by a refactor PR (#2) here, in tpchgen/src/text.rs, but not used since.

[clflushopt]

👍

Addressed in #141