Fix true/TRUE

Ruby 2.7 defined the uppercase constants, but Ruby 3 doesn't anymore.

Author: adangel

lib/pmdtester/builders/project_hasher.rb

@@ -111,7 +111,7 @@ def violation_type(violation)
       end
     end
 
-    def make_violation_hash(file_ref, violation, is_diff = TRUE)
+    def make_violation_hash(file_ref, violation, is_diff = true)
       h = {
         't' => is_diff ? violation_type(violation) : '+',
         'l' => violation.line,