remove hacks to circumvent IOCapture hang

[musoke]

9857ede introduced some hacks to circumvent a hang when using Documenter to run doc tests.

In particular, remove these lines:

WolframExpr.jl/.github/workflows/CI.yml

Line 84 in 9857ede

using MathLink; W`Sin`;

WolframExpr.jl/docs/Project.toml

Line 3 in 9857ede

MathLink = "18c93696-a329-5786-9845-8443133fa0b4"

WolframExpr.jl/docs/make.jl

Lines 3 to 7 in 9857ede

	using MathLink
	# Prevent IOCapture from hanging within doctests
	# See https://github.com/JuliaDocs/IOCapture.jl/issues/17
	W`Sin`

WolframExpr.jl/test/runtests.jl

Lines 4 to 8 in 9857ede

	using MathLink
	# Prevent IOCapture from hanging within doctests
	# See https://github.com/JuliaDocs/IOCapture.jl/issues/17
	W`Sin`

Depends on JuliaDocs/IOCapture.jl#17