patchDocumentation: use brackets for optional arguments

> The documentation for git blame used vertical bars for optional
> arguments to -M and -C, which is unusual and potentially confusing.
> Since most man pages use brackets for optional items, and that's
> consistent with how we document the same options for git diff and
> friends, use brackets here, too.

>
> Signed-off-by: brian m. carlson <sandals@crustytoothpaste.net>
> ---
>  Documentation/blame-options.txt | 4 ++--
>  1 file changed, 2 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/blame-options.txt b/Documentation/blame-options.txt
> index 2669b87c9d..dc41957afa 100644
> --- a/Documentation/blame-options.txt
> +++ b/Documentation/blame-options.txt
> @@ -77,7 +77,7 @@ include::line-range-format.txt[]
>  	terminal. Can't use `--progress` together with `--porcelain`
>  	or `--incremental`.
>  
> --M|<num>|::
> +-M[<num>]::
>  	Detect moved or copied lines within a file. When a commit
>  	moves or copies a block of lines (e.g. the original file
>  	has A and then B, and the commit changes it to B and then
> @@ -93,7 +93,7 @@ alphanumeric characters that Git must detect as moving/copying
>  within a file for it to associate those lines with the parent
>  commit. The default value is 20.
>  
> --C|<num>|::
> +-C[<num>]::
>  	In addition to `-M`, detect lines moved or copied from other
>  	files that were modified in the same commit.  This is
>  	useful when you reorganize your program and move code