Bump external/glad from 2ae8255 to 8dc0d4d

Bumps [external/glad](https://github.com/Dav1dde/glad) from `2ae8255` to `8dc0d4d`.
- [Release notes](https://github.com/Dav1dde/glad/releases)
- [Commits](Dav1dde/glad@2ae8255...8dc0d4d)

---
updated-dependencies:
- dependency-name: external/glad
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>