[R][CI] Fix test-r-linux-as-cran job by pulling in dev cpp11

[amoeba]

Describe the bug, including details regarding any error messages, version, and platform.

With #45606 merged, the test-r-linux-as-cran job will always fail due to r-lib/cpp11#448. Once the cpp11 PR is merged, we can pull that in to fix the job.

Component(s)

R, Continuous Integration

[amoeba]

I don't think we ever saw the CI failure we expected but I've filed a PR to remove the whitespace from our last remaining instance since it seems like a good thing to do.

[amoeba]

There was already a PR for the change in #46949 so I've closed the latter and will merge the former.