Fix brew link (#303)

## What
SSIA

## CHECKS ⚠️

Please make sure you are aware of the following.

- [x] **The changes in this PR doesn't have private information

Author: uki-a

document/01-git.en.md

@@ -22,7 +22,7 @@ In this step, we will learn how to use Git and GitHub.
    $ git version
    ```
 
-   * For Mac users: Install [brew](https://brew.sh/index) and `brew install git`
+   * For Mac users: Install [brew](https://brew.sh/) and `brew install git`
    * For Windows users: Download [installer](https://gitforwindows.org/)
 
 2. Set your name and email address using git config. Check if your email address shows up.

document/01-git.ja.md

@@ -22,7 +22,7 @@
    $ git version
    ```
 
-   * Macを使っている場合: [brew](https://brew.sh/index_ja) をインストールしてから `brew install git`を実行
+   * Macを使っている場合: [brew](https://brew.sh/ja/) をインストールしてから `brew install git`を実行
    * For Windows user: Download [installer](https://gitforwindows.org/)
 
 2. git configに自分の名前とemailアドレスを設定します。以下のコマンドを実行して最後にあなたのemailアドレスが表示されればOKです。