[ruby/prism] Revert "Merge pull request ruby#3606 from tenderlove/clear-flags"

This reverts commit ruby/prism@4052d93cf852, reversing
changes made to ruby/prism@47143d17b3f7.

ruby/prism@f117ec6354

Author: k0kubun

prism/prism.c

@@ -5279,10 +5279,6 @@ pm_interpolated_string_node_append(pm_interpolated_string_node_t *node, pm_node_
 
     switch (PM_NODE_TYPE(part)) {
         case PM_STRING_NODE:
-            // If inner string is not frozen, clear flags for this string
-            if (!PM_NODE_FLAG_P(part, PM_STRING_FLAGS_FROZEN)) {
-                CLEAR_FLAGS(node);
-            }
             part->flags = (pm_node_flags_t) ((part->flags | PM_NODE_FLAG_STATIC_LITERAL | PM_STRING_FLAGS_FROZEN) & ~PM_STRING_FLAGS_MUTABLE);
             break;
         case PM_INTERPOLATED_STRING_NODE:

test/prism/result/static_literals_test.rb

@@ -4,11 +4,6 @@
 
 module Prism
   class StaticLiteralsTest < TestCase
-    def test_concatenanted_string_literal_is_not_static
-      node = Prism.parse_statement("'a' 'b'")
-      refute_predicate node, :static_literal?
-    end
-
     def test_static_literals
       assert_warning("1")
       assert_warning("0xA", "10", "10")