Fix incorrect supportsUserOperations expectation for server-to-server credentials.

[leogdion]

⚠️ Potential issue | 🟠 Major

Fix incorrect supportsUserOperations expectation for server-to-server credentials.

TokenCredentials.supportsUserOperations returns false for .serverToServer (see Sources/MistKit/Authentication/TokenCredentials.swift, Lines 36-48), so this assertion will always fail. Update the expectation to reflect the actual behavior.

Based on learnings

🤖 Prompt for AI Agents

In
Tests/MistKitTests/Authentication/Protocol/TokenManagerTokenCredentialsTests.swift
around lines 75 to 83, the test incorrectly expects server-to-server credentials
to support user operations; TokenCredentials.supportsUserOperations returns
false for .serverToServer. Update the test expectation to assert
serverCredentials.supportsUserOperations == false (instead of true) so the test
matches the implementation.

Originally posted by @coderabbitai[bot] in #105 (comment)