Require `ipykernel` in Positron #1423

Job	Run time
OS=macOS-latest R=release py=3.11	4m 7s
OS=windows-latest R=release py=3.11	7m 33s
OS=ubuntu-latest R=release py=3.11	4m 34s
OS=macOS-latest R=oldrel py=3.11	4m 9s
OS=ubuntu-latest R=oldrel-1 py=3.10	6m 16s
OS=ubuntu-latest R=oldrel-2 py=3.10	4m 43s
OS=ubuntu-20.04 R=oldrel-3 py=3.9	4m 58s
OS=ubuntu-20.04 R=oldrel-4 py=3.9	4m 58s
OS=ubuntu-latest R=release py=3.8	5m 54s
OS=ubuntu-latest R=release py=3.9	4m 32s
OS=ubuntu-latest R=release py=3.11	5m 21s
OS=ubuntu-latest R=release py=3.12	4m 58s
OS=ubuntu-latest R=release py=3.13	4m 41s
OS=ubuntu-latest R=devel py=3.13	6m 14s
	1h 12m 58s

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