Fix Python 3 error in particle sample in 1.9

direct/src/particles/ParticleEffect.py

@@ -200,7 +200,7 @@ class ParticleEffect(NodePath):
 
     def loadConfig(self, filename):
         data = vfs.readFile(filename, 1)
-        data = data.replace('\r', '')
+        data = data.replace(b'\r', b'')
         try:
             exec(data)
         except: