[Java] [Native] Remove trailing slashes from the baseUri

[Gama11]

Otherwise, you can end up with double slashes, e.g. https://example.com//path. Some severs are actually ok with that, but you can't rely on it.

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[wing328]

Thanks for the PR. Is this similar to #7940?

Which OpenAPI Generator version are you using?

[Gama11]

I'm using version 5.1.1.

That PR does seem somewhat related, but it appears to only remove trailing slashes from the URLs declared within the "hardcoded" servers in the OpenAPI YML file. That doesn't help with the use case we have, where we set a custom baseUri (which may or may not have a traliling slash) via the ApiClient constructor.