doesn't show all backedges

the following code should print `all_backedges` but it only prints one. Not sure what's wrong

```julia-repl
1.9.0-beta4>using MethodAnalysis

1.9.0-beta4>mi = methodinstances(@which issorted([1, 3, 2]))[1]
MethodInstance for issorted(::Vector{UInt32})

1.9.0-beta4>println(mi)
MethodInstance for issorted(::Vector{UInt32})

1.9.0-beta4>direct_backedges(mi) # also loaded from MethodAnalysis.jl

1-element Vector{Core.MethodInstance}:
MethodInstance for unique!(::Vector{UInt32})

1.9.0-beta4>

1.9.0-beta4>all_backedges(mi)
1-element Vector{Core.MethodInstance}:
MethodInstance for unique!(::Vector{UInt32})
```

In tim's case it shows `all_backedges`

Reproduce the Julia REPL example using `methodinstances`, `direct_backedges`, and `all_backedges` from MethodAnalysis. Trace why `all_backedges(mi)` returns only `unique!(::Vector{UInt32})`, and consider the issue complete when it reports all expected backedges, including those shown in the referenced example.

Written by the indexing model from the issue text.