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.

1993/ant/README.md

@@ -23,7 +23,7 @@ For more detailed information see [1993 ant in bugs.md](/bugs.md#1993-ant).
 ```
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

1993/dgibson/README.md

@@ -16,7 +16,7 @@ where:
 `datafile` is the initial pattern (default: [dgibson.data1](dgibson.data1))
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh

1993/schnitzi/README.md

@@ -30,7 +30,7 @@ where
 Certain input will cause the program to fail as described in the bugs.md file.
 
 
-### Try:
+## Try:
 
 ```sh
 ./schnitzi schnitzi.info

1993/vanb/README.md

@@ -26,7 +26,7 @@ where `exp` is an octal expression. See below for how it can also have
 hexadecimal and decimal numbers.
 
 
-### Try:
+## Try:
 
 ```sh
 ./try.sh