change xz to gz

[johnbuhay]

Describe the bug
mise or asdf is requesting a file that doesn't exist
see the cloudflare-go releases page for available assets

Steps to reproduce

mise use [email protected] --verbose
[DEBUG] ARGS: /home/REDACTED/.local/bin/mise use [email protected] --verbose
[DEBUG] Config {
    Config Files: [
        "~/.config/mise/config.toml",
    ],
}
[DEBUG] Toolset: [email protected]
downloading
~/.local/share/mise/plugins/flarectl/bin/download
[DEBUG] $ ~/.local/share/mise/plugins/flarectl/bin/download
* Downloading flarectl release 0.85.0...
curl: (22) The requested URL returned error: 404
asdf-flarectl: Could not download https://github.com/cloudflare/cloudflare-go/releases/download/v0.85.0/flarectl_0.85.0_linux_amd64.tar.xz
[ERROR] ~/.local/share/mise/plugins/flarectl/bin/download failed
Error:
   0: ~/.local/share/mise/plugins/flarectl/bin/download exited with non-zero status: exit code 1

Location:
   /rustc/82e1608dfa6e0b5569232559e3d385fea5a93112/library/core/src/convert/mod.rs:757

Version:
   2024.1.30 linux-x64 (3a195bc 2024-01-27)

Suggestion: Run with --verbose or MISE_VERBOSE=1 for more information.

Backtrace omitted. Run with RUST_BACKTRACE=1 environment variable to display it.
Run with RUST_BACKTRACE=full to include source snippets.

Expected behavior

flarectl should successfully install
mise or asdf should retrieve the gz file