Breaking change to `Pair` under broadcast

[MasonProtter]

This may require a git-bisect or a blame to figure out when it happened, but here's an upper and lower bound to start:

julia> sin.(0 => π)
2-element Array{Float64,1}:
 0.0                   
 1.2246467991473532e-16

julia> VERSION
v"1.1.1"

vs

julia> sin.(0 => π)
ERROR: MethodError: no method matching sin(::Pair{Int64, Irrational{:π}})
[...]

julia> VERSION
v"1.6.5"

[MasonProtter]

Apparently this was intentional: #32209