Fix Abolish Council Tax has no budgetary impact #1153 (#1154)

Author: nikhilwoodruff

changelog_entry.yaml

@@ -0,0 +1,4 @@
+- bump: patch
+  changes:
+    fixed:
+    - Abolish Council Tax has no budgetary impact.

policyengine_uk/variables/gov/gov_tax.py

@@ -34,3 +34,12 @@ class gov_tax(Variable):
         "high_income_incident_tax_change",
         "ni_employer",
     ]
+
+    def formula(household, period, parameters):
+        variables = list(gov_tax.adds)
+        if parameters(period).gov.contrib.abolish_council_tax:
+            variables = [
+                variable for variable in variables if variable != "council_tax"
+            ]
+
+        return add(household, period, variables)