databases/R-cran-RSQLite: Update to 2.3.6

While I'm here,

- remove conditionals regarding llvm16 build fix as port build fine
  without it.
- add test target

ChangeLog: https://cran.r-project.org/web/packages/RSQLite/news/news.html

Differential Revision:	https://reviews.freebsd.org/D44592