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.

1985/applin/README.md

@@ -5,7 +5,7 @@ make all
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./applin

1985/august/README.md

@@ -12,7 +12,7 @@ make all
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

1985/lycklama/README.md

@@ -15,7 +15,7 @@ To see why we recommend the alternate version instead of the original version,
 see below and the [Original code](#original-code) section.
 
 
-### Try:
+## Try:
 
 This alternate version, which we recommend you you try first, prior to the
 original, slows down the output so that you can see what it looked like back in 1985.

1985/sicherman/README.md

@@ -21,7 +21,7 @@ echo foo | ./sicherman
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh