Install PG15 in homebrew test

The homebrew tap for timescaledb has been switched to PG15 but
the default postgres in the macos github environment is PG14 so
we have to explicitly install PG15.

.github/workflows/homebrew.yaml

@@ -26,6 +26,8 @@ jobs:
 
     - name: Setup
       run: |
+        brew install postgresql@15
+        echo "/usr/local/opt/postgresql@15/bin" >> $GITHUB_PATH
         brew tap timescale/tap
         brew info timescaledb
 
@@ -34,7 +36,7 @@ jobs:
         brew install timescaledb ${{ matrix.install_options }}
         timescaledb-tune --quiet --yes
         timescaledb_move.sh
-        brew services start postgresql
+        brew services start postgresql@15
 
     # checkout code to get version information
     - uses: actions/checkout@v3