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.

1984/laman/README.md

@@ -12,7 +12,7 @@ make all
 ```
 
 
-### Try:
+## Try:
 
 The program accepts ONE POSITIVE number.  Seeing is believing, so try things
 like:

1984/mullender/README.md

@@ -46,7 +46,7 @@ BTW: is there such a thing as too fast a CPU ? :-) Actually yes for certain code
 which is probably not as uncommon as you think :-).
 
 
-### Try:
+## Try:
 
 ```sh
 ./mullender.alt