fixed typo in error message for Rational{BigInt} constructor (#35575)

Author: chrstphrbrns

base/irrationals.jl

@@ -51,7 +51,7 @@ Complex{T}(x::AbstractIrrational) where {T<:Real} = Complex{T}(T(x))
         p += 32
     end
 end
-(::Type{Rational{BigInt}})(x::AbstractIrrational) = throw(ArgumentError("Cannot convert an AbstractIrrational to a Rational{BigInt}: use rationalize(Rational{BigInt}, x) instead"))
+(::Type{Rational{BigInt}})(x::AbstractIrrational) = throw(ArgumentError("Cannot convert an AbstractIrrational to a Rational{BigInt}: use rationalize(BigInt, x) instead"))
 
 @pure function (t::Type{T})(x::AbstractIrrational, r::RoundingMode) where T<:Union{Float32,Float64}
     setprecision(BigFloat, 256) do