Add history entry

Author: pblowey

HISTORY.rst

@@ -7,6 +7,7 @@ Unreleased
 - Minimum supported python is now 3.11.
 - Switch python packaging backend back to setuptools. (`#263 <https://github.com/DiamondLightSource/python-zocalo/pull/263>`_)
 - ``zocalo.dlq_purge``: Show which queues DLQ messages came from, and accept queue names with prefix. (`#264 <https://github.com/DiamondLightSource/python-zocalo/pull/264>`_)
+- Allow default zocalo environment to be set by environment variable `ZOCALO_DEFAULT_ENV`. This takes priority over default in `ZOCALO_CONFIG` file (`#267 <https://github.com/DiamondLightSource/python-zocalo/pull/267>`_)  
 
 1.2.0 (2024-11-14)
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