Require newer knitr and rmarkdown everywhere

[infotroph]

Hopefully for real this time: Fixes xfun::isFALSE deprecation warnings by updating knitr and rmarkdown to versions that use base::isFALSE internally.

Note that as wirtten, the check and renderbook jobs will fail one more time on this PR:

• The current build of the depends image is in an inconsistent state where {knitr} is still old but {xfun} has already been updated to a newer version that complains when you use an old {knitr}.
• Therefor the check job is going to fail because pecan.depends.R tries to install BioCro (and fails because the old knitr can't compile its vignettes) before it gets to the line that will update knitr. 😞
• If the Docker CI job passes, it should be OK to merge this with the other checks failing. That will bring the depends image back into a version-consistent state.
• Once that deployment finishes and the depends image rebuilds overnight, the next round of package checks should be able to compile BioCro (and all of PEcAn) without error again.

Description

Motivation and Context

Review Time Estimate

• [ ] Immediately
• [ ] Within one week
• [ ] When possible

Types of changes

• [ ] Bug fix (non-breaking change which fixes an issue)
• [ ] New feature (non-breaking change which adds functionality)
• [ ] Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• [ ] My change requires a change to the documentation.
• [ ] My name is in the list of CITATION.cff
• [ ] I have updated the CHANGELOG.md.
• [ ] I have updated the documentation accordingly.
• [ ] I have read the CONTRIBUTING document.
• [ ] I have added tests to cover my changes.
• [ ] All new and existing tests passed.