Fix heading level of 'Try' section

It was agreed to be '## Try:' but there were many files where it was
'### Try:'. This has been corrected.

2011/richards/README.md

@@ -23,7 +23,7 @@ For more detailed information see [2011 richards in bugs.md](/bugs.md#2011-richa
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 echo '10 9 8 7 6 5 4 3 2 1*p*p*p*p*p*p*p*p*p' | ./richards