Remove Proto Definitions of `desugar_jdk_libs_apis.proto`
Remove Proto Definitions of `desugar_jdk_libs_apis.proto`

- Unused in the current `AndroidJdkLibsChecker`
- Follow-up of https://github.com/google/error-prone/commit/cb09495bbbe3b97db71287662e9ce0ea81825390

PiperOrigin-RevId: 438141485

google/error-prone,google/error-prone