BUG: tuple default argument representation

[larsoner]

Describe the bug
Documenting a function with def func(x=(1, 2)) shows up as def func(x=1, 2) when processed by Sphinx.

According to a git bisect this regression was introduced by c4d7f4d

To Reproduce
From numpy/numpydoc#291, steps to reproduce the behavior:

$ git clone https://github.com/larsoner/numpydoc
$ cd numpydoc
$ git checkout -b tuple origin/tuple
$ cd numpydoc/tests/tinybuild
$ make
<click on my_function in the built doc that pops up>

Screenshots

On commit 822625d (correct):

On commit c4d7f4d (incorrect):

Environment info

• OS: Linunx
• Python version: 3.8
• Sphinx version: above
• Sphinx extensions: numpydoc, autodoc, autosummary

[larsoner]

Looks like this was fixed by #8265