Copyedit doc/whatsnew additions from #371

- Subsections for specific modules follow general list.
- Remove leading indent.
- Omit .model prefix from :mod:`…` links.
- Use nested lists for 2+ changes to the same submodule.
- Explain the acronym 'MCM', since this does not appear elsewhere in the
  documentation.

Author: khaeru

doc/whatsnew.rst

@@ -4,17 +4,6 @@ What's new
 Next release
 ============
 
-  Water/Nexus
-  -----------
-  
-  - Update :doc:`/water/index` with unit standardization from Km^3 to MCM and model size reduction (:pull:`371`).
-  - Deactivate share calibration constraints for cooling water technologies (:pull:`371`).
-  - Fix excess vintage activity year generation in :mod:`.model.water.utils` to reduce model size (:pull:`371`).
-  - Add missing electricity input units for water technologies in :mod:`.model.water.data.infrastructure` (:pull:`371`).
-  - Fix incorrect data for desalination projected capacity in :mod:`.model.water.data.infrastructure` (:pull:`371`).
-  - Add missing basins_country_R12.csv data file to :mod:`.model.water.data` (:pull:`371`).
-  - Convert Excel data files to CSV format and add improve test coverage for :mod:`.model.water.data` (:pull:`371`).
-
 - Improve and extend :doc:`/material/index` (:pull:`388`),
   specifically :mod:`.material.data_steel`.
   See :doc:`/material/v1.2.0` for details.
@@ -36,6 +25,23 @@ Next release
 
 - Add 23 technologies used in |ssp-scenariomip| to :ref:`technology-yaml` (:pull:`378`).
 
+Water/Nexus
+-----------
+
+- Update :doc:`/water/index` with unit standardization from km³
+  to 10⁶ m³ (million cubic metres, or MCM) and model size reduction (:pull:`371`).
+- Deactivate share calibration constraints for cooling water technologies (:pull:`371`).
+- Fix excess vintage activity year generation in :mod:`.water.utils` to reduce model size (:pull:`371`).
+- Improve :mod:`.water.data` (:pull:`371`):
+
+  - Add missing :file:`basins_country_R12.csv` data file.
+  - Convert Excel data files to CSV format and add/improve test coverage.
+
+- Improve :mod:`.water.data.infrastructure` (:pull:`371`):
+
+  - Add missing electricity input units for water technologies.
+  - Fix incorrect data for desalination projected capacity.
+
 v2025.7.23
 ==========