Set PG_MAX_VER globally in CI

Author: JelteF

.github/workflows/build_and_test.yaml

@@ -59,6 +59,9 @@ jobs:
 
     runs-on: ubuntu-24.04
 
+    env:
+      PG_MAX_VER: "19"
+
     steps:
       - name: Test details
         run: echo Build and test pg_duckdb with PostgreSQL ${{ matrix.version }} branch
@@ -133,7 +136,7 @@ jobs:
       - name: Build pg_duckdb extension
         id: build
         working-directory: duckdb
-        run: ERROR_ON_WARNING=1 make -j8 install DUCKDB_BUILD=${{ matrix.type }} PG_MAX_VER=19
+        run: ERROR_ON_WARNING=1 make -j8 install DUCKDB_BUILD=${{ matrix.type }}
 
       - name: Run make installcheck
         id: installcheck