patchFix minor typo in mergetool.txt: 'overwriten' -> 'overwritten'

> From: Noah Betzen <noah@nezteb.net>
>
> Signed-off-by: Noah Betzen <noah@nezteb.net>
> ---
>     Fix minor typo in mergetool.txt
>     
>     I only learned of mergetool.hideResolved today, and while reading the
>     docs I noticed a tiny typo, so I figured I'd fix it.

>
> Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1350%2FNezteb%2Fpatch-1-v1
> Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1350/Nezteb/patch-1-v1
> Pull-Request: https://github.com/git/git/pull/1350
>
>  Documentation/config/mergetool.txt | 2 +-
>  1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/Documentation/config/mergetool.txt b/Documentation/config/mergetool.txt
> index 90b38097002..e779a122d8a 100644
> --- a/Documentation/config/mergetool.txt
> +++ b/Documentation/config/mergetool.txt
> @@ -59,7 +59,7 @@ mergetool.hideResolved::
>  	possible and write the 'MERGED' file containing conflict markers around
>  	any conflicts that it cannot resolve; 'LOCAL' and 'REMOTE' normally
>  	represent the versions of the file from before Git's conflict
> -	resolution. This flag causes 'LOCAL' and 'REMOTE' to be overwriten so
> +	resolution. This flag causes 'LOCAL' and 'REMOTE' to be overwritten so
>  	that only the unresolved conflicts are presented to the merge tool. Can
>  	be configured per-tool via the `mergetool.<tool>.hideResolved`
>  	configuration variable. Defaults to `false`.
>
> base-commit: bcd6bc478adc4951d57ec597c44b12ee74bc88fb