Update specutils requirement from <=1.12.*,>=1.9.* to >=1.9.0.a,<=1.12.0

Updates the requirements on [specutils](https://github.com/astropy/specutils) to permit the latest version.
- [Release notes](https://github.com/astropy/specutils/releases)
- [Changelog](https://github.com/astropy/specutils/blob/main/CHANGES.rst)
- [Commits](astropy/specutils@v1.9.0...v1.12.0)

---
updated-dependencies:
- dependency-name: specutils
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

requirements.txt

@@ -9,4 +9,4 @@ pyvo>=1.4.1, <=1.4.2
 regions==0.7
 requests>=2.4.3
 seaborn >=0.12.*, <=0.13.*
-specutils<=1.12.*, >=1.9.*
+specutils>=1.9.0.a, <=1.12.0