@wip fix dumb BB error

`removeAllPhis` untracking *all* its phis from the CFG, not the ones you actually removed.

src/main/java/org/prlprg/ir/cfg/BB.java

@@ -679,7 +679,7 @@ public void removeAllPhis(Collection<? extends Phi<?>> phis) {
     if (this.phis.size() != oldSize - phis.size()) {
       throw new IllegalArgumentException("Not all in " + id() + ": " + phis);
     }
-    cfg().untrackAll(this.phis);
+    cfg().untrackAll(phis);
 
     cfg().record(new CFGEdit.RemovePhis(this, phis), new CFGEdit.InsertPhis(this, phis));
   }