Update installation.md
Update installation.md

Added a note that the install process requires Git on the server to successfully complete.

iwzh/laravel-doc-offline,xpressengine/laravel-korean-docs,iwzh/laravel-docs,xpressengine/laravel-korean-docs,ryanwinchester/laravel-docs,tusharvikky/docs,khs1994-gitbook/laravel-docs,ryanwinchester/laravel-docs,chenrenzhen/laravel-docs-china,tusharvikky/docs,laravel-china/laravel-docs