fix: install remotes package for R CI test (#3037)

## Summary
- `devtools` 2.5.0+ requires `remotes` to be installed separately for
`install_deps()` to work
- Adds `remotes` to the R test workflow install step

## Test plan
- [x] R 4.4.1 CI job passes

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: talsperre

.github/workflows/test.yml

@@ -81,7 +81,7 @@ jobs:
         python3 -m venv path/to/venv
         source path/to/venv/bin/activate
         python3 -m pip install .
-        Rscript -e 'install.packages("devtools", repos="https://cloud.r-project.org", Ncpus=8)'
+        Rscript -e 'install.packages(c("devtools", "remotes"), repos="https://cloud.r-project.org", Ncpus=8)'
         Rscript -e 'devtools::install_deps("R", dependencies=TRUE, repos="https://cloud.r-project.org", upgrade="default")'
         R CMD INSTALL R
         Rscript -e 'install.packages(c("data.table", "caret", "glmnet", "Matrix", "rjson"), repos="https://cloud.r-project.org", Ncpus=8)'