ci: use docker tidyverse of R v3.6.3 instead of r-base

Refs #18
2 jobs for 18-try-tidyverse-docker-image-for-ci in 6 minutes and 34 seconds (queued for 11 seconds)
Status Name Job ID Coverage
  Checks
failed check_as_cran #137507
docker

00:06:23

failed check_not_cran #137506
docker

00:06:19

 
Name Stage Failure
failed
check_as_cran Checks
E>   ‘V03_First_Calibration.Rmd’ ‘V04_Open-loop_influenced_flow.Rmd’
E> ‘V05_Open-loop_influenced_flow_calibration.Rmd’
E>
E> Error: Vignette re-building failed.
E> Execution halted

Execution halted
Cleaning up file based variables
ERROR: Job failed: exit code 1
failed
check_not_cran Checks
E>   ‘V03_First_Calibration.Rmd’ ‘V04_Open-loop_influenced_flow.Rmd’
E> ‘V05_Open-loop_influenced_flow_calibration.Rmd’
E>
E> Error: Vignette re-building failed.
E> Execution halted

Execution halted
Cleaning up file based variables
ERROR: Job failed: exit code 1