[FIX] partially revert 3e2e1d6b90

One of the behavioural divergences between "create or replace" view and
DROP; CREATE turns out to be that "create or replace" can only add
columns *at the end* of the view, and can not change the name or type of
the view during replacement, which can break migrations.

Reinstate the old drop;create as replacement is not necessary for this
specific view.

addons/crm/report/crm_opportunity_report.py

@@ -49,8 +49,9 @@ class OpportunityReport(models.Model):
     medium_id = fields.Many2one('utm.medium', string='Medium', readonly=True)
 
     def init(self):
+        tools.drop_view_if_exists(self._cr, 'crm_opportunity_report')
         self._cr.execute("""
-            CREATE OR REPLACE VIEW crm_opportunity_report AS (
+            CREATE VIEW crm_opportunity_report AS (
                 SELECT
                     c.id,
                     c.date_deadline,