Bump mvdan/shfmt from v3.8.0 to v3.9.0 in /.github/linting (#92)

Bumps mvdan/shfmt from v3.8.0 to v3.9.0.

---
updated-dependencies:
- dependency-name: mvdan/shfmt
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>
Co-authored-by: dependabot[bot] <49699333+dependabot[bot]@users.noreply.github.com>
Co-authored-by: James Curtin <jameswcurtin@gmail.com>

.github/linting/Dockerfile

@@ -1,4 +1,4 @@
-FROM mvdan/shfmt:v3.8.0 as shfmt
+FROM mvdan/shfmt:v3.9.0 as shfmt
 FROM koalaman/shellcheck:v0.10.0 as shellcheck
 
 FROM python:3.11.3-alpine3.16