[doc] downgrade ipython version from 9.12.0 to 9.10.1

cannot rebuild the docs with latest ipython

Author: nutrik

doc/requirements.txt

@@ -3,7 +3,7 @@ entrypoints==0.4
 Pillow==12.2.0
 Sphinx==9.0.4
 furo==2025.12.19
-ipython==9.12.0
+ipython==9.10.1
 h5py==3.15.1
 h5netcdf==1.8.1
 xarray==2026.2.0