Fix link to discussion board

[jeffreytolar]

Noticed this on https://squidfunk.github.io/mkdocs-material/bug-report/#related-links, where

Additionally, since you have searched our issue tracker and discussion board before reporting an issue, and have possibly found several issues or discussions, include those as well.

has both links pointing to the same page.

The bug issue template does use the right URLs:

mkdocs-material/.github/ISSUE_TEMPLATE/bug.yml

Lines 37 to 38 in c8fb426

	thoroughly read it. Additionally, list links to possibly related [issues](https://github.com/squidfunk/mkdocs-material/issues)
	or [discussions](https://github.com/squidfunk/mkdocs-material/discussions)

[squidfunk]

Good catch, certainly a copy+paste error.