Fix up tables (1 of 2)

[gewarren]

Contributes to #4328.

Preview links:

https://review.docs.microsoft.com/en-us/dotnet/api/system.double.compareto?view=netcore-3.1&branch=pr-en-us-4329#System_Double_CompareTo_System_Object_

https://review.docs.microsoft.com/en-us/dotnet/api/system.math.clamp?view=netcore-3.1&branch=pr-en-us-4329#System_Math_Clamp_System_Double_System_Double_System_Double_

https://review.docs.microsoft.com/en-us/dotnet/api/system.nullable-1.equals?view=netcore-3.1&branch=pr-en-us-4329

https://review.docs.microsoft.com/en-us/dotnet/api/system.single.compareto?view=netcore-3.1&branch=pr-en-us-4329#System_Single_CompareTo_System_Object_

[tdykstra]

LGTM. Many of these are virtually unreadable blocks of non-indented XML and I made a suggestion for one showing how much more readable it is with formatting, but it's probably not worth the effort to do that on all of them.