[C++][Parquet] Remove obsolete generated files

### Describe the enhancement requested

When bumping Thrift to v0.19.0, it seems we left two obsolete files in the repository: `src/generated/parquet_constants.h` and `src/generated/parquet_constants.cpp` (both are marked as "Autogenerated by Thrift Compiler (0.13.0)").

### Component(s)

C++, Parquet