Auto merge of #16150 - kdy1997:master, r=jdm

Allow using servo as dependency, by fixing Cargo.toml of servo-test-t…

- [ ] `./mach build -d` does not report any errors
I had hard time trying to compile rust-mozjs on my ubuntu machine, and I gave up. As this pr does not touch any source code, I expect it to be work.

- [x] `./mach test-tidy` does not report any errors

```sh
Checking the config file...
Checking directories for correct file extensions...

tidy reported no errors.
```

- [x] These changes fix #16149 (github issue number if applicable).

- [x] These changes do not require tests because it's trivial.

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python/tidy/servo_tidy_tests/Cargo.toml

@@ -6,3 +6,6 @@ publish = false
 
 [dependencies]
 test-package = { version = "*" }
+
+[lib]
+path = "lib.rs"