Define `rem_edge!(::AbstractGraph, ::Pair)`

[mtfishman]

I was surprised to see that rem_edge!(::AbstractGraph, ::Pair) isn't defined:

julia> using Graphs

julia> g = path_graph(4)
{4, 3} undirected simple Int64 graph

julia> rem_edge!(g, 2 => 3)
ERROR: MethodError: no method matching rem_edge!(::SimpleGraph{Int64}, ::Pair{Int64, Int64})

Closest candidates are:
  rem_edge!(::SimpleGraph{T}, ::Graphs.SimpleGraphs.SimpleEdge{T}) where T
   @ Graphs ~/.julia/packages/Graphs/czpTe/src/SimpleGraphs/simplegraph.jl:519
  rem_edge!(::Graphs.SimpleGraphs.AbstractSimpleGraph{T}, ::Integer, ::Integer) where T
   @ Graphs ~/.julia/packages/Graphs/czpTe/src/SimpleGraphs/SimpleGraphs.jl:183

Stacktrace:
 [1] top-level scope
   @ REPL[5]:1

julia> add_edge!(g, 1 => 3)
true

julia> using Pkg; Pkg.status("Graphs")
Status `/private/var/folders/qz/q22pzwm144z9fq57mpf1hfp40000gq/T/jl_gltxtS/Project.toml`
  [86223c79] Graphs v1.10.0

[gdalle]

If only for symmetry reasons, I'd accept a PR adding the method. Wanna do it?