This deletes `projects/select-row-locking/`, the working folder of the
row locking project. Everything in it now lives somewhere permanent, so
nothing is lost.

Row locks on a select shipped in two pull requests:

```ts
await tx.orm.public.Product.where({ id }).forUpdate().first();
// SELECT ... FOR UPDATE OF "product"
```

- #30549 gave the typed SQL builder `forUpdate()`, `forNoKeyUpdate()`,
`forShare()` and `forKeyShare()`.
- #30555 gave the ORM client the same methods, and closed #30531.

Where the folder's content went:

- The design is ADR 261, merged in #30542.
- `packages/2-sql/4-lanes/sql-builder/STATUS.md` lists row locking as
supported.
- `docs/reference/capabilities.md` documents the seven capabilities.
- The follow-up work is filed in Linear as TML-3492, TML-3493, TML-3494
and TML-3495.

No other file in the repo refers to the folder.

Agent: crusoe-92

Signed-off-by: willbot <w.a.madden+machine@gmail.com>
Signed-off-by: Will Madden <madden@prisma.io>