Rust: Remove "thread::scoped" snippet
Rust: Remove "thread::scoped" snippet

`thread::scoped` no longer exists.

phatograph/vim-snippets,needle-wang/vim-snippets,craigp/vim-snippets,adam-e-trepanier/vim-snippets,honza/vim-snippets,craigp/vim-snippets,adam-e-trepanier/vim-snippets,needle-wang/vim-snippets,kevinkirkup/vim-snippets,kevinkirkup/vim-snippets,phatograph/vim-snippets,honza/vim-snippets