build(deps): update astropy requirement

Updates the requirements on [astropy](https://github.com/astropy/astropy) to permit the latest version.
- [Release notes](https://github.com/astropy/astropy/releases)
- [Changelog](https://github.com/astropy/astropy/blob/main/docs/changelog.rst)
- [Commits](astropy/astropy@v6.1.2...v7.0.0)

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

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

requirements.txt

@@ -1,4 +1,4 @@
-astropy>=6.1.2,<6.2.0
+astropy>=6.1.2,<7.1.0
 ipython>=8.27.0,<8.30.0
 matplotlib>=3.9.1,<3.10.0
 numpy>=2.1.0,<2.2.0