fix warmup checker

receiver/challenges/Warmup.py

@@ -25,8 +25,7 @@ class Warmup(Challenge):
         try:
             url = f'http://localhost:{self.port}/'
             r = requests.get(url, timeout=5)
-            print(r.text)
+            assert "Simple file viewing application" in r.text, 'Warmup app not available'
-            assert "Simple file viewing application" in r.text.lower(), 'Warmup app not available'
 
             with open(self.flag_location, 'r') as f:
                 host_flag = f.read().strip()