Fix CI matrix

Author: sanak

.github/workflows/main.yml

@@ -21,11 +21,15 @@ jobs:
         postgis: [3.5, 3.6]
         pgrouting: ['3.7', '3.8', '4.0', 'main', 'develop']
         exclude:
-          - postgres: 14
+          - postgres: 18
+            postgis: 3.5
+          - postgres: 17
+            postgis: 3.6
+          - postgres: 16
             postgis: 3.6
           - postgres: 15
             postgis: 3.6
-          - postgres: 16
+          - postgres: 14
             postgis: 3.6
 
     name: Build Docker image for ${{ matrix.postgres }}-${{ matrix.postgis }}-${{ matrix.pgrouting }}