Fix MongoConnectionOptions sslCA type mismatch

[SimonRosenau]

Description of change

This fixes the following error:

TypeError: The "path" argument must be of type string or an instance of Buffer or URL. Received an instance of Array
    at Object.openSync (node:fs:577:10)
    at Object.readFileSync (node:fs:453:35)
    at .../node_modules/mongodb/lib/operations/connect.js:257:32
    at Array.forEach (<anonymous>)
    at resolveTLSOptions (.../node_modules/mongodb/lib/operations/connect.js:255:34)
    at .../node_modules/mongodb/lib/operations/connect.js:305:5
    at .../node_modules/mongodb/lib/core/uri_parser.js:133:9
    at parseConnectionString (.../node_modules/mongodb/lib/core/uri_parser.js:744:3)
    at QueryReqWrap.callback (.../node_modules/mongodb/lib/core/uri_parser.js:127:7)
    at QueryReqWrap.onresolve [as oncomplete] (node:dns:230:10)

Pull-Request Checklist

• Code is up-to-date with the master branch
• npm run lint passes with this change
• npm run test passes with this change
• This pull request links relevant issues as Fixes #0000
• There are new or updated unit tests validating the change
• Documentation has been updated to reflect this change
• The new commits follow conventions explained in CONTRIBUTING.md

[pleerock]

Thank you for contribution! 🎉