Using ML metadata postgres SSL connection options don't work for `sslMode=require`

Checked with both `1.14.0` and `1.15.0.dev20230814` versions of mlmd Docker images.

Trying to use Postgres SSL configuration options with `sslMode=require` causes the following error:
```
WARNING: Logging before InitGoogleLogging() is written to STDERR
I1122 01:34:29.953503 1 postgresql_metadata_source.cc:208] Connecting to database.
E1122 01:34:29.953600 1 postgresql_metadata_source.cc:211] PostgreSQL error: sslmode value "require" invalid when SSL support is not compiled in
F1122 01:34:29.953652 1 metadata_store_server_main.cc:555] Check failed: absl::OkStatus() == status (OK vs. INTERNAL: PostgreSQL metadata source error: connection pointer is NULL
) MetadataStore cannot be created with the given connection config.
*** Check failure stack trace: ***
```

Searching the error on the web suggests that the `libpq` library included in mlmd Docker image was not compiled with `--with-openssl` configure option.

Is this an issue in the image, or are we missing some other option when using the Docker image?