Update R kernel installation, remove dependency on r studio CDN #149

Job	Run time
build-template / Build E2B Template	9m 43s
charts-tests / Chart Data Extractor - Build and test	27s
js-sdk / JS SDK - Build and test	2m 40s
python-sdk / Python SDK - Build and test	8m 29s
cleanup-build-template / Cleanup Build Template	14s
	21m 33s

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