rm irrelevant entries from .gitignore; fixes #10609

.gitignore

@@ -13,8 +13,6 @@ _site
 *.zip
 *.vi
 *~
-*.sass-cache
-*.ruby-version
 
 # OS or Editor folders
 .DS_Store
@@ -28,6 +26,7 @@ Thumbs.db
 nbproject
 *.sublime-project
 *.sublime-workspace
+.idea
 
 # Komodo
 *.komodoproject
@@ -38,8 +37,4 @@ validation-status.json
 validation-report.json
 
 # Folders to ignore
-.hg
-.svn
-.CVS
-.idea
 node_modules