build(deps): bump app_units from 0.7.1 to 0.7.3 (#30135)

Bumps [app_units](https://github.com/servo/app_units) from 0.7.1 to 0.7.3.
- [Release notes](https://github.com/servo/app_units/releases)
- [Commits](https://github.com/servo/app_units/commits/v0.7.3)

---
updated-dependencies:
- dependency-name: app_units
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>

Cargo.lock

@@ -148,9 +148,9 @@ checksum = "3b13c32d80ecc7ab747b80c3784bce54ee8a7a0cc4fbda9bf4cda2cf6fe90854"
 
 [[package]]
 name = "app_units"
-version = "0.7.1"
+version = "0.7.3"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "fc3ec9d4c47b25a5a9e5c848e053640331c7cedb1637434d75db68b79fee8a7f"
+checksum = "34655f9657fbb59fdd430438ba907566eb2d90b7fb0410d488d8ddabcd7b2cc9"
 dependencies = [
  "num-traits",
  "serde",