Fix CI failures on oldrel-4 (i.e. R 3.5)

[yutannihilation]

Currently the CI fails with this error:

   Error: 
  ! error in pak subprocess
  Caused by error: 
  ! Cannot install packages:
  * deps::.: Can't install dependency quantreg
  * quantreg: Can't install dependency MatrixModels
  * MatrixModels: Needs R >= 3.6.0

This pull request bumps the version of ignore-before-r for quantreg, and remove unnecessary ignore-before-r as the oldest one is now R 3.5.

Also, it seems warnPartialMatchArgs did not accept FALSE at the time of R 3.5. So this pull request skips the tests on R < 3.6.

══ Failed tests ════════════════════════════════════════════════════════════════
── Error (???): geom_quantile matches quantile regression ──────────────────────
Error in `options(old_options)`: invalid value for 'warnPartialMatchArgs'
Backtrace:
    ▆
 1. └─withr (local) `<fn>`(`<env>`)

[ FAIL 1 | WARN 0 | SKIP 77 | PASS 1846 ]

[yutannihilation]

@thomasp85 @clauswilke @karawoo
Sorry to bother you, can anyone approve this to fix the CI?

[karawoo]

lgtm, thanks!

[yutannihilation]

Thanks for approving!!