Typo in certificate spelling

Just fixed certificate spelling in instructions.

app.py

@@ -349,7 +349,7 @@ Upon completion of {EXAM_MAX_QUESTIONS} questions, you can collect and share you
 ## Instructions
 1. Log in then click 'Start' to begin. 
 2. Answer each question and click 'Next' 
-3. Click 'Claim your certificae' to get a certificate and share it with the world! 🌍"
+3. Click 'Claim your certificate' to get a certificate and share it with the world! 🌍"
 
 ## Questions:
 """)