[guppy] fix bug with package renamed to self #1208

Job	Run time
Build documentation (ubuntu-latest)	1m 1s
Cross-compile to aarch64	2m 38s
Build and test core crates (ubuntu-latest, 1.75)	2m 20s
Build and test (all features) (ubuntu-latest, 1.75)	2m 59s
Build and test core crates (ubuntu-latest, stable)	1m 48s
Build and test (all features) (ubuntu-latest, stable)	3m 43s
Lint	1m 47s
cargo-compare extended tests (ubuntu-latest)	4m 56s
Build and test core crates (macos-14, 1.75)	3m 8s
Build and test (all features) (macos-14, 1.75)	2m 39s
cargo-compare extended tests (macos-14)	4m 50s
Build and test core crates (macos-14, stable)	1m 34s
Build and test (all features) (macos-14, stable)	3m 54s
Build and test core crates (windows-latest, 1.75)	5m 18s
Build and test (all features) (windows-latest, 1.75)	6m 23s
Build and test core crates (windows-latest, stable)	5m 12s
Build and test (all features) (windows-latest, stable)	5m 26s
	59m 36s

Provide feedback