Fix `manual_let_else` and `single_match_else` lints #2575

Job	Run time
docs	24s
msrv	50s
minimal	18s
check-cfg	23s
quickchecking	24s
rustfmt-clippy	27s
test (ubuntu-latest, 9.0, 1, 0, 0, 0, 0)	1m 51s
test-book	6s
test (ubuntu-latest, 9.0, 1, 0, 0, 1, 0)	2m 10s
test-expectations (ubuntu-latest)	50s
test-expectations (macos-12)	1m 21s
test (ubuntu-latest, 9.0, 1, 0, 1, 0, 0)	1m 42s
test (ubuntu-latest, 9.0, 1, 0, 1, 1, 0)	1m 40s
test (ubuntu-latest, 9.0, 1, 1, 0, 0, 0)	2m 15s
test (ubuntu-latest, 9.0, 1, 1, 0, 1, 0)	2m 8s
test (ubuntu-latest, 9.0, 1, 1, 1, 0, 0)	2m 11s
test (ubuntu-latest, 9.0, 1, 1, 1, 1, 0)	2m 8s
test (ubuntu-latest, 16.0, 1, 0, 0, 0, 0)	4m 46s
test (ubuntu-latest, 16.0, 1, 0, 0, 1, 0)	3m 58s
test (ubuntu-latest, 16.0, 1, 0, 1, 0, 0)	4m 20s
test (ubuntu-latest, 16.0, 1, 0, 1, 1, 0)	3m 54s
test (ubuntu-latest, 16.0, 1, 1, 0, 0, 0)	4m 50s
test (ubuntu-latest, 16.0, 1, 1, 0, 1, 0)	4m 50s
test (ubuntu-latest, 16.0, 1, 1, 1, 0, 0)	4m 34s
test (ubuntu-latest, 16.0, 1, 1, 1, 1, 0)	4m 51s
test (ubuntu-latest, 16.0, 0, 0, 1)	1m 54s
test (macos-12, 9.0, 0, 0, 0)	1m 48s
success	1s
	1h 0m 54s

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