Ensure rustfmt is invoked without edition parameter #295

Job	Run time
test (ubuntu-latest, 29.4)	1m 0s
test (ubuntu-latest, 27.2)	49s
test (ubuntu-latest, 26.3)	38s
test (macos-latest, 28.2)	2m 34s
test (macos-latest, 29.4)	2m 36s
test (ubuntu-latest, 30.1)	1m 40s
test (macos-latest, 30.1)	2m 32s
test (windows-latest, 26.3)	2m 20s
test (ubuntu-latest, snapshot, true)	48s
test (windows-latest, 28.2)	1m 39s
test (windows-latest, snapshot, true)	2m 23s
test (windows-latest, 30.1)	2m 19s
test (ubuntu-latest, 28.2)	58s
test (macos-latest, snapshot, true)	2m 33s
test (windows-latest, 27.2)	2m 19s
test (windows-latest, 29.4)	1m 41s
	28m 49s

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