`_decimal` leaks references

[neonene]

Bug report

Bug description:

The following leaks can be seen since a43cc3f, fb0d9b9:

>python -X showrefcount -c "import _decimal"
[7117 refs, 4232 blocks] 

CPython versions tested on:

3.13, CPython main branch

Operating systems tested on:

Windows

Linked PRs

• gh-123243: Fix reference leak in _decimal #123244
• [3.13] gh-123243: Fix reference leak in _decimal (GH-123244) #123280