fix(chartutil): corrected spelling in doc block

pkg/chartutil/expand.go

@@ -72,7 +72,7 @@ func Expand(dir string, r io.Reader) error {
 	return nil
 }
 
-// ExpandFile expands the src file into the dest directroy.
+// ExpandFile expands the src file into the dest directory.
 func ExpandFile(dest, src string) error {
 	h, err := os.Open(src)
 	if err != nil {