update matrix

Author: ImreSamu

.github/workflows/buildx.yml

@@ -34,15 +34,15 @@ jobs:
         #
         # succesful tests matrix:
         platforms: ['linux/arm64','linux/arm/v7','linux/arm/v6','linux/386','linux/ppc64le']
-        postgres: ['15beta3']
+        postgres: ['15beta4']
         postgis: ['3.2']
         variant: [alpine]
         include:
-          - postgres: '15beta3'
+          - postgres: '15beta4'
             postgis: '3.2'
             variant: 'default'
             platforms: 'linux/arm64'
-          - postgres: '15beta3'
+          - postgres: '15beta4'
             postgis: '3.2'
             variant: 'default'
             platforms: 'linux/ppc64le'