Remove NFMDP_PE_LoadHints group from all class libraries

### Details about Task

**nanoFramework area:** class libraries

### Description
`NFMDP_PE_LoadHints` aren't required anymore. Need to remove the respective ItemGroup from all class libraries. See [here](https://github.com/nanoframework/System.IO.FileSystem/commit/00d3a6c9fe8fa4c33ffbffc60633e7f9885cb664) for reference.