build(deps): bump app_units from 0.7.7 to 0.7.8 (#35889)

Bumps [app_units](https://github.com/servo/app_units) from 0.7.7 to 0.7.8.
- [Release notes](https://github.com/servo/app_units/releases)
- [Commits](https://github.com/servo/app_units/compare/v0.7.7...v0.7.8)

---
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

@@ -211,9 +211,9 @@ checksum = "dcfed56ad506cb2c684a14971b8861fdc3baaaae314b9e5f9bb532cbe3ba7a4f"
 
 [[package]]
 name = "app_units"
-version = "0.7.7"
+version = "0.7.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "cc864acc81f608e316133cd6bfb67ac57c11503a8cd54c55a818dd6b506abee5"
+checksum = "467b60e4ee6761cd6fd4e03ea58acefc8eec0d1b1def995c1b3b783fa7be8a60"
 dependencies = [
  "num-traits",
  "serde",