Remove overzealous permission change post-install

Allows group-writeable Ruby installations

Reverts e1b50e6

Fix rbenv#400, close rbenv#903

bin/ruby-build

@@ -214,7 +214,6 @@ make_package() {
   before_install_package "$package_name"
   build_package "$package_name" $*
   after_install_package "$package_name"
-  fix_directory_permissions
   popd >&4
 }
 
@@ -772,11 +771,6 @@ after_install_package() {
   local stub=1
 }
 
-fix_directory_permissions() {
-  # Ensure installed directories are not world-writable to avoid Bundler warnings
-  find "$PREFIX_PATH" -type d \( -perm -020 -o -perm -002 \) -exec chmod go-w {} \;
-}
-
 fix_rbx_gem_binstubs() {
   local prefix="$1"
   local gemdir="${prefix}/gems/bin"