Fix loop scaling when removing a block (#72134)

Fix loop scaling when removing a block (#72134)

Due to very odd, stress-induced flow graph, on x86, the fall-through
predecessor block to an empty (but not unreachable) block was a
"catch" handler that was not reachable from the block's target (since
"catch" blocks don't have predecessors).

However, the code in fgRemoveBlock that was calling optScaleLoopBlocks
didn't make any sense, and removing it causes no diffs. So get rid of it.

Fixes #64764