refact(sensitivity): instead of count query use rowcount to get numbe…

…r of removed sensitivity rule (#3323)

backend/geonature/core/sensitivity/utils.py

@@ -132,8 +132,4 @@ def insert_sensitivity_referential(source, csvfile):
 
 def remove_sensitivity_referential(source):
     whereclause = SensitivityRule.source == source
-    count_source = db.session.scalar(
-        sa.select(sa.func.count()).where(whereclause),
-    )
-    db.session.execute(sa.delete(SensitivityRule).where(whereclause))
-    return count_source
+    return db.session.execute(sa.delete(SensitivityRule).where(whereclause)).rowcount