Warn about the use of non-generic collections

**Is your feature request related to a problem? Please describe.**

I'm an F# newbie and was working with some existing code that used `hashtable` which is non-generic. I was given some advice to use `Dictionary` instead by to be careful to not open `System.Collections` because it contains a non-generic version of `Dictionary`.

**Describe the solution you'd like**

As an F# newbie it would be nice if the compiler warned about this sort of thing.

**Describe alternatives you've considered**

I could try creating an FSharpLint rule for this.

**Additional context**

N/A