install pgdump for ci

Author: Amogh-Bharadwaj

.github/workflows/flow.yml

@@ -125,11 +125,16 @@ jobs:
           go-version: '1.26.2'
           cache-dependency-path: flow/go.sum
 
-      - name: install lib-geos
+      - name: install lib-geos and pg_dump
         run: |
           # No need to update man pages on package install
           sudo apt-get remove --purge man-db
-          sudo apt-get install libgeos-dev
+          sudo apt-get update
+          sudo apt-get install -y libgeos-dev
+          # pg_dump must be >= the server major version; install v18 so it
+          # can dump PG 16, 17, and 18 (backward compatible).
+          sudo apt-get install -y postgresql-client-18
+          echo /usr/lib/postgresql/18/bin >> $GITHUB_PATH
 
       - name: install retry tool
         run: |