ci(deps): update `gitfast` to its new structure (#12922)

Co-authored-by: Carlo Sala <carlosalag@protonmail.com>

.github/dependencies.yml

@@ -5,8 +5,10 @@ dependencies:
     version: tag:v2.1
     postcopy: |
       set -e
-      rm -rf git-completion.plugin.zsh Makefile README.adoc t tools
-      test -e git-completion.zsh && mv -f git-completion.zsh _git
+      rm -rf git-completion.plugin.zsh Makefile t tools
+      mv README.adoc MANUAL.adoc
+      mv -f src/* .
+      rmdir src
   plugins/gradle:
     repo: gradle/gradle-completion
     branch: master