fix: Add comma for "move if to guard"

[weirane]

As I mentioned in #11017, there is a little issue in the implementation for if branch. This code

let y = match 92 {
    x => {
        if x == 0 {$0
            false
        }
    }
    _ => true,
};

will be transformed to

let y = match 92 {
    x if x == 0 => false
    _ => true,
};

a comma is missing after the false. I moved the fix from the code handling else branch to above.

[Veykril]

Thanks!
bors r+

[bors]

Build succeeded:

• Rust (macos-latest)
• Rust (ubuntu-latest)
• Rust (windows-latest)
• TypeScript (ubuntu-latest)
• TypeScript (windows-latest)