Fix dictionary key lookup in Module.update(parameters:)

[gzink]

Proposed changes

Fix incorrect dictionary key lookup in Module.update(parameters:verify:).
In the .dictionary, .dictionary case of the recursive apply function, values[key] uses the parent path component instead of values[dictionaryKey] (the current child key). This causes all parameters in [String: Module] or [String: MLXArray] dictionary properties to be silently skipped during updates.

-        if let valueItem = values[key] {
+        if let valueItem = values[dictionaryKey] {

Added testDictionaryParameters regression test in ModuleTests.swift.
Fixes #362

Checklist

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• I have read the CONTRIBUTING document
• I have run pre-commit run --all-files to format my code / installed pre-commit prior to committing changes (swift-formatter instead)
• I have added tests that prove my fix is effective or that my feature works
• I have updated the necessary documentation (if needed)

[davidkoski]

That is a really good find, thank you!