Bump celery-haystack-ng to 2.0 to support batch update tasks

CHANGELOG.rst

@@ -31,6 +31,7 @@ Fixed
 * The ``Person`` model had an ``is_active`` flag that was used in unclear ways; it is now removed
 * The data check results list view didn't work if a related object had been deleted in the meanwhile.
 * Socialaccount login template was not overriden
+* Atomic transactions now cause only one Haystack update task to run
 
 Changed
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pyproject.toml

@@ -94,7 +94,7 @@ django-guardian = "^2.2.0"
 rules = "^3.0"
 django-cache-memoize = "^0.1.6"
 django-haystack = "^3.1"
-celery-haystack-ng = "^0.21.1"
+celery-haystack-ng = "^2.0"
 django-dbbackup = "^3.3.0"
 spdx-license-list = "^0.5.0"
 license-expression = "^21.6"