fix postgres drivers tests related to custom granularities

Author: KSDaemon

packages/cubejs-testing-drivers/fixtures/_schemas.json

@@ -93,12 +93,13 @@
           "granularities": [
             {
               "name": "half_year",
-              "interval": "6 months"
+              "interval": "6 months",
+              "origin": "2024-01-01"
             },
             {
               "name": "half_year_by_1st_april",
               "interval": "6 months",
-              "offset": "3 months"
+              "origin": "2024-04-01"
             },
             {
               "name": "two_mo_by_feb",
@@ -119,12 +120,13 @@
           "granularities": [
             {
               "name": "half_year",
-              "interval": "6 months"
+              "interval": "6 months",
+              "origin": "2024-01-01"
             },
             {
               "name": "half_year_by_1st_april",
               "interval": "6 months",
-              "offset": "3 months"
+              "origin": "2024-04-01"
             },
             {
               "name": "two_mo_by_feb",