Hi, All.

CRAN instability seems to be a blocker for our dev process.
The following simple check causes consecutive failures in 4 of 9 Jenkins jobs + PR builder.

- spark-branch-2.4-test-sbt-hadoop-2.6
- spark-branch-2.4-test-sbt-hadoop-2.7
- spark-master-test-sbt-hadoop-2.7
- spark-master-test-sbt-hadoop-3.2
- PRBuilder

* checking CRAN incoming feasibility ...Error in .check_package_CRAN_incoming(pkgdir) : 
  dims [product 24] do not match the length of object [0]

Since this happens frequently and it's out of our control,
I'd like to suggest remove this R check from the above main Jenkins jobs.
Instead, like `linter` or `snapshot publish` jobs, we can have independent Jenkins jobs for R CRAN incoming feasibility check.

How do you think about that?