Missed Optimization: Fold x - umin(x,13) < 2 into single compare x < 15

```
define i1 @src(i64 %arg0) {
%v0 = tail call i64 @llvm.umin.i64(i64 %arg0, i64 13)
%v1 = sub nsw i64 %arg0, %v0
%v2 = icmp slt i64 %v1, 2
ret i1 %v2
}

define i1 @tgt(i64 %arg0) {
%v0 = icmp slt i64 %arg0, 15
ret i1 %v0
}
```
alive2: https://alive2.llvm.org/ce/z/pyUQAP
godbolt: https://godbolt.org/z/TaYWM9GTe
Pattern found in: https://github.com/dtcxzyw/llvm-opt-benchmark/blob/main/bench/ffmpeg/optimized/pictordec.ll