Remove submodule unshallowing #28

Job	Run time
extension	43s
build	1m 13s
test (ubuntu-latest)	8m 3s
test (windows-latest)	11m 28s
test (no submodules)	1m 45s
test (noembed)	2m 28s
format	1m 25s
generate	1m 57s
test (macos-latest)	4m 47s
test (concurrent test programs)	6m 42s
test (race mode)	1s
lint (windows-latest)	9m 5s
lint (ubuntu-latest)	1m 33s
smoke	2m 21s
lint (noembed)	2m 46s
lint (macos-latest)	1m 22s
misc	37s
baselines	3m 57s
tidy	36s
required	2s
	1h 2m 51s

Provide feedback