zig fmt should not be opt-out

[BenFradella]

This option should be disabled by default.

vim-polyglot/ftplugin/zig.vim

Line 59 in f5393cf

autocmd BufWritePre <buffer> if get(g:, 'zig_fmt_autosave', 1) | call zig#fmt#Format() | endif

[idbrii]

That's how it is on the original plugin so it won't change here:

https://github.com/ziglang/zig.vim/blob/master/ftplugin/zig.vim#L53-L56

It's already reported there: ziglang/zig.vim#51