l10n: zh_CN: Update Git Glossary: fork

Remove "复刻" from translation option list of "fork", keeping "派生" as the only one. In Git context, by talking about the term "fork", one usually mean the procedure that divides a branch into two or more history lines. That is quite like the "fork" concept in programming, which split a process into two or more independent processes. On the other hand, "复刻" by itself means "copy" or "mirror". It is considered more suitable for describing the procedure like "fork a repository", which is common on public repository hosting services, such as GitHub. However, this is beyond the scope of core-Git. As a l10n work for core-Git, "复刻" should be removed here. There used to be another option - "分岔". Its a good idea to translate "fork point" as "分岔点". However, "派生点" is as good, too. So this option is finally discarded. Also fix a relevant translation issue which was introduced in `160fb2b`. Signed-off-by: Ray Chen <oldsharp@gmail.com>