Call EnsureNothingConflictsWithGrep() when opening a new file

[gabebw]

It needs to run after vim/after/ftplugin/*.vim because that can set key bindings:

https://github.com/gabebw/dotfiles/blob/0da5afdf96c90b08181c1c79911cfd98fca9457f/vim/after/ftplugin/typescriptreact.vim#L28

Here's an idea that doesn't work:

autocmd BufReadPost call EnsureNothingConflictsWithGrep()

It seems like BufReadPost doesn't run late enough.