fix: Avoids compiler crash on open source MacOS

[NeedleInAJayStack]

This resolves a compiler crasher on open-source 6.1 and 6.2 toolchains on MacOS. There was apparently some resolution problem with some Collection<NodeAndCommands> that was fixed by making the type concrete [ValkeyServerAddress: NodeAndCommands].Values. This function is internal and only used in one call site, which required no changes.

Closes #250

[adam-fowler]

Yeah I guess I don't need the some Collection here given it is an internal function

[codecov-commenter]

Codecov Report

❌ Patch coverage is 0% with 1 line in your changes missing coverage. Please review.
⚠️ Please upload report for BASE (main@40c2ad0). Learn more about missing BASE report.

Files with missing lines	Patch %	Lines
Sources/Valkey/Cluster/ValkeyClusterClient.swift	0.00%	1 Missing ⚠️

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #251   +/-   ##
=======================================
  Coverage        ?   40.92%           
=======================================
  Files           ?       94           
  Lines           ?    15785           
  Branches        ?        0           
=======================================
  Hits            ?     6460           
  Misses          ?     9325           
  Partials        ?        0           

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.

🚀 New features to boost your workflow:

• ❄️ Test Analytics: Detect flaky tests, report on failures, and find test suite problems.