[llvm] Delete the incorrect assert that assumes size of `APFloat` is the same as `IEEEFloat`. (PR #111780)

[Matt Arsenault via llvm-commits]

arsenm wrote:

> The issue is that APFloat has a union (`Storage`). Downstream this includes a member / field for another floating point type. 

So the assert isn't wrong if you're actually changing the type downstream. If you're changing the type downstream you have to also change the assert downstream 

https://github.com/llvm/llvm-project/pull/111780