lsp-start-plain: fix path that can contain spaces #5455

Job	Run time
test (ubuntu-latest, 27.2, false)	1m 58s
test (ubuntu-latest, 28.2, false)	2m 41s
test (ubuntu-latest, 29.4, false)	2m 28s
test (macos-latest, 28.2, false)	3m 42s
test (macos-latest, 29.4, false)	3m 43s
test (windows-latest, 27.2, false)	3m 5s
test (windows-latest, 28.2, false)	3m 37s
test (windows-latest, 29.4, false)	3m 21s
test (ubuntu-latest, snapshot, true)	1m 24s
test (macos-latest, snapshot, true)	2m 53s
test (windows-latest, snapshot, true)	6m 52s
	35m 44s

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