RFR: 8287766: Unnecessary Vector usage in LdapClient

[Andrey Turbanov]

On Sun, 29 May 2022 20:22:55 GMT, Andrey Turbanov <aturbanov at openjdk.org> wrote:

> In [JDK-8273098](https://bugs.openjdk.java.net/browse/JDK-8273098) I missed one place, where Vector could be replaced with ArrayList.
> Usage of thread-safe collection `Vector` is unnecessary. It's recommended to use `ArrayList` if a thread-safe implementation is not needed.

Thank you for review!

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PR: https://git.openjdk.java.net/jdk/pull/8940