chore: 更新「git filter-repo：高效率的 Git 版控庫歷史重寫工具」子主題

Signed-off-by: 林博仁(Buo-ren Lin) <[email protected]>

.gitmodules

@@ -23,10 +23,6 @@
 	path = gitignore - A collection of useful .gitignore templates
 	url = https://github.com/github/gitignore.git
 	ignore = dirty
-[submodule "Unofficial Snap Packaging for git filter-repo"]
-	path = Unofficial Snap Packaging for git filter-repo
-	url = https://github.com/brlin-tw/git-filter-repo-snap.git
-	ignore = dirty
 [submodule "vcsh-git: 林博仁(Buo-ren Lin)'s preferred Git configuration"]
 	path = vcsh-git: 林博仁(Buo-ren Lin)'s preferred Git configuration
 	url = https://github.com/brlin-tw/vcsh-git.git

README.md

@@ -74,8 +74,6 @@ Git 版本控制系統<ruby>修訂歷史<rp>(</rp><rt>history</rt><rp>)</rp></ru
   提供多種情境適用之 Git 版本追蹤忽略規則
 * [gitignore - A collection of useful .gitignore templates](https://github.com/github/gitignore)  
   由 GitHub 所維護的多情境適用之 Git 追蹤排除規則範本
-* [Unofficial Snap Packaging for git filter-repo](https://github.com/brlin-tw/git-filter-repo-snap)  
-  於支援 Snap 的 Linux 作業系統上提供即可用的 `git filter-repo` 軟體
 * [vcsh-git](https://github.com/brlin-tw/vcsh-git)  
   林博仁(Buo-ren Lin)'s preferred Git configuration
 * [git filter-repo](https://gitlab.com/libre-knowledge/git-filter-repo)