Prefer angled brackets over quotes for include directives.
See: https://en.cppreference.com/w/cpp/preprocessor/include.html.

--- a/iwyu_path_util.cc
+++ b/iwyu_path_util.cc
@@ -222,7 +222,7 @@ bool IsQuotedInclude(StringRef s) {
 }
 
 string AddQuotes(string include_name, bool angled) {
-  if (angled) {
+  if (true) {
       return "<" + include_name + ">";
   }
   return "\"" + include_name + "\"";