Bump simple-plist from 1.1.1 to 1.3.1 in /TestingApp

Bumps [simple-plist](https://github.com/wollardj/simple-plist) from 1.1.1 to 1.3.1.
- [Release notes](https://github.com/wollardj/simple-plist/releases)
- [Commits](wollardj/simple-plist@v1.1.1...v1.3.1)

---
updated-dependencies:
- dependency-name: simple-plist
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <[email protected]>