fix: Remove platform checking logic for Windows

[averageCryptoNerd]

Windows doesn't natively support bash scripts, therefore there is no need to check if the platform contains Windows. A full changelog is below.

• Removed Windows-x64 from supported targets
• Removed fallback unzip/curl logic used only for Windows

[rekram1-node]

Did you read the original pr? https://github.com/sst/opencode/pull/2100

windows users using git bash can use this script to install