JIT: flow opts does an incorrect pred list update

[AndyAyersMS]

Repro case is:

// Generated by Fuzzlyn v1.2 on 2021-07-07 08:13:57
// Seed: 11738605779775786426
// Reduced from 155.0 KiB to 0.5 KiB in 00:30:58
// Crashes the runtime
public class Program
{
 static bool s_1;
 public static void Main()
 {
 ulong vr1 = 0;
 for (int vr2 = 0; vr2 < 0; vr2++)
 {
 if (s_1)
 {
 try
 {
 }
 finally
 {
 vr1 = vr1;
 }
 }
 else
 {
 if (s_1)
 {
 bool vr3 = s_1;
 }
 }
 }
 }
}

and it leads to a jit assert

Assert failure(PID 20200 [0x00004ee8], Thread: 24136 [0x5e48]): Assertion failed 'i < BitSetTraits::GetSize(env)' 
 in 'Program:Main()' during 'Compute blocks reachability' (IL size 41)

See #56184 (comment) and following comments for more details.