Remove unnecessary check of line number

[yuyichao]

Reapply the other half of #59971

Apparently the debug info can still be useful even when the line number is invalid (i.e. function name).

Curretly this seems to occur with callback in single line comprehensions.

---

Although I don't have the exact system to reproduce, the backtrace in questions is likely sth like,

 [1] throw_complex_domainerror(f::Symbol, x::Float64)
   @ Base.Math ./math.jl:33
 [2] sqrt
   @ ./math.jl:645 [inlined]
 [3] #sqrteach##0
   @ ./none:-1 [inlined]
 [4] iterate
   @ ./generator.jl:48 [inlined]
 [5] collect_to!(dest::Vector{…}, itr::Base.Generator{…}, offs::Int64, st::Int64)
   @ Base ./array.jl:886

Where the callback from the comprehension doesn't have a line number. This is confirmed with,

julia> sqrteach(a) = [sqrt(x) for x in a]
sqrteach (generic function with 1 method)

julia> @code_lowered debuginfo=:source sqrteach([1.0])
CodeInfo(
    @ REPL[1]:1 within `unknown scope`
1 ─ %1 = Main.:(var"#sqrteach##0#sqrteach##1")
│        #4 = %new(%1)
│   %3 = #4
│   %4 =   dynamic Base.Generator(%3, a)
│   %5 =   dynamic Base.collect(%4)
└──      return %5
)

julia> cb = Main.:(var"#sqrteach##0#sqrteach##1").instance
#sqrteach##0 (generic function with 1 method)

julia> @code_lowered debuginfo=:source cb(1.0)
CodeInfo(
1 ─ %1 = Main.sqrt
│   %2 =   dynamic (%1)(x)
└──      return %2
)

In any case though, there is probably still cases where the line number is missing for some frames where the function name is available so this can still be useful.