Remove devdeps312 from tox; sklearn now has py312 nightly wheel

tox.ini

@@ -1,6 +1,6 @@
 [tox]
 envlist =
-    py{39,310,311,312}-test{,-alldeps,-devdeps,-devdeps312,-oldestdeps,-devinfra}{,-cov}
+    py{39,310,311,312}-test{,-alldeps,-devdeps,-oldestdeps,-devinfra}{,-cov}
     py{39,310,311,312}-test-numpy{122,123,124,125,126}
     build_docs
     linkcheck
@@ -17,7 +17,6 @@ isolated_build = true
 setenv =
     MPLBACKEND=agg
     devdeps: PIP_EXTRA_INDEX_URL = https://pypi.anaconda.org/scientific-python-nightly-wheels/simple https://pypi.anaconda.org/astropy/simple
-    devdeps312: PIP_EXTRA_INDEX_URL = https://pypi.anaconda.org/scientific-python-nightly-wheels/simple https://pypi.anaconda.org/astropy/simple
 
 # Pass through the following environment variables which may be needed
 # for the CI
@@ -75,14 +74,6 @@ deps =
     devdeps: astropy>=0.0.dev0
     devdeps: git+https://github.com/spacetelescope/gwcs.git
 
-    # scikit-learn Python 3.12 wheel is not available yet
-    devdeps312: numpy>=0.0.dev0
-    devdeps312: scipy>=0.0.dev0
-    devdeps312: scikit-image>=0.0.dev0
-    devdeps312: matplotlib>=0.0.dev0
-    devdeps312: astropy>=0.0.dev0
-    devdeps312: git+https://github.com/spacetelescope/gwcs.git
-
     # Latest developer version of infrastructure packages.
     devinfra: git+https://github.com/pytest-dev/pytest.git
     devinfra: git+https://github.com/astropy/extension-helpers.git
@@ -104,7 +95,6 @@ commands =
     # Force numpy-dev after matplotlib downgrades it
     # (https://github.com/matplotlib/matplotlib/issues/26847)
     devdeps: python -m pip install --pre --upgrade --extra-index-url https://pypi.anaconda.org/scientific-python-nightly-wheels/simple numpy
-    devdeps312: python -m pip install --pre --upgrade --extra-index-url https://pypi.anaconda.org/scientific-python-nightly-wheels/simple numpy
     pip freeze
     pytest --pyargs photutils {toxinidir}/docs \
     cov: --cov photutils --cov-config={toxinidir}/pyproject.toml --cov-report xml:{toxinidir}/coverage.xml --cov-report term-missing \