chore(tox): Drop mpl from x86, old numpy constraint

tox.ini

@@ -73,7 +73,7 @@ set_env =
 extras =
   test
 
-  # Simple, thanks pillow
+  # Simple, thanks Hugo and Paul
   !none: dicomfs
   !none: indexed_gzip
 
@@ -89,14 +89,10 @@ extras =
   py3{9,10,11,12,13}-{min,full,pre-dev}-{x,arm}64: minc2
   py3{9,10,11,12,13}-{min,full,pre-dev}-{x,arm}64: zstd
 
-  # No win32 wheels for scipy/matplotlib after py39
+  # No win32 wheels for scipy after py39
   py39-full-x86: spm
-  py39-full-x86: viewers
 
 deps =
-  # Numpy 2.0 is a major breaking release; we cannot put much effort into
-  # supporting until it's at least RC stable
-  dev: numpy >=2.1.dev0
   dev: pydicom @ git+https://github.com/pydicom/pydicom.git@main
 
 uv_resolution =