Fix compile errors when using this package with a pre-2024 version of Wwise

[fadookie]

We are using Wwise 2023 and this package would not compile with the following errors:

Library/PackageCache/com.audiokinetic.wwise.addressables@9ea57a5b65/Runtime/AkAddressableBankManager.cs(176,87): error CS0103: The name 'bank' does not exist in the current context
Library/PackageCache/com.audiokinetic.wwise.addressables@9ea57a5b65/Runtime/AkAddressableBankManager.cs(177,32): error CS0103: The name 'bank' does not exist in the current context
Library/PackageCache/com.audiokinetic.wwise.addressables@9ea57a5b65/Runtime/AkAddressableBankManager.cs(177,70): error CS0103: The name 'bank' does not exist in the current context
Library/PackageCache/com.audiokinetic.wwise.addressables@9ea57a5b65/Runtime/AkAddressableBankManager.cs(185,32): error CS0103: The name 'bank' does not exist in the current context

This PR fixes the compilation errors, but I have not yet been able to functional testing with Wwise 2023.