eliminate relative paths from Cargo.toml #622

Job	Run time
lint	3m 47s
Rust unit tests (ubuntu-latest)	4m 41s
docs	2m 23s
Rust unit tests (macos-latest)	4m 51s
coverage	5m 4s
Rustfmt	13s
Rust unit tests (windows-latest)	5m 43s
test (macos-latest, 3.8)	11m 10s
typecheck	2m 43s
test (macos-latest, 3.9)	8m 35s
test (macos-latest, 3.10)	12m 39s
test (macos-latest, 3.11)	9m 15s
test (macos-latest, 3.12-dev)	11m 2s
test (ubuntu-latest, 3.8)	7m 4s
test (ubuntu-latest, 3.9)	5m 52s
test (ubuntu-latest, 3.10)	6m 3s
test (ubuntu-latest, 3.11)	7m 58s
test (ubuntu-latest, 3.12-dev)	7m 30s
test (windows-latest, 3.8)	8m 13s
test (windows-latest, 3.9)	7m 59s
test (windows-latest, 3.10)	7m 17s
test (windows-latest, 3.11)	13m 41s
test (windows-latest, 3.12-dev)	11m 10s
	2h 44m 53s

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