Documentation for `Enumerable.ToDictionary` refers to inapplicable concept of "groups"

### Type of issue

Other (describe below)

### Description

The docs for a couple of overloads of `ToDictionary` state:

> The values within each group are in the same order as in source.

The concept of "group" doesn't apply to this operation, and that sentence looks like it might be left over after copying the docs for `ToLookup`.

It also suggests there's some kind of guarantee about the order of items in the resulting `Dictionary`, when that type makes no ordering guarantees.

### Page URL

https://learn.microsoft.com/en-us/dotnet/api/system.linq.enumerable.todictionary?view=net-8.0

### Content source URL

https://github.com/dotnet/dotnet-api-docs/blob/main/xml/System.Linq/Enumerable.xml

### Document Version Independent Id

58d09d91-dc91-5480-8c81-f13a0c8eb2a5

### Article author

@dotnet-bot