go/types, types2: remove unnecessary assert on pointer size

As described in #61249, uncommon pointer sizes do exist. Remove an
unnecessary assertion.

Fixes #61249

Change-Id: Ib15857bd6bcd42ec530817a132bb8db036236c3b
Reviewed-on: https://go-review.googlesource.com/c/go/+/508821
Reviewed-by: Robert Griesemer <[email protected]>
Auto-Submit: Robert Findley <[email protected]>
Run-TryBot: Robert Findley <[email protected]>
TryBot-Result: Gopher Robot <[email protected]>

Author: findleyr

src/cmd/compile/internal/types2/const.go

@@ -73,7 +73,6 @@ func representableConst(x constant.Value, check *Checker, typ *Basic, rounded *c
 
 	sizeof := func(T Type) int64 {
 		s := conf.sizeof(T)
-		assert(s == 4 || s == 8)
 		return s
 	}