vim-til: file name typo

[gnanet]

@jbranchaud The line below is referencing vim/turning-off-search-highlighting.md

til/README.md

Line 1342 in 711310b

- [Turning Off Search Highlighting](vim/turning-off-search-highlighting.md)

but the file in that folder is missing an f and is called vim/turning-of-search-highlighting.md

Suggested fix is to rename vim/turning-of-search-highlighting.md -> vim/turning-off-search-highlighting.md