Changing heading level of 'Alternate code'

Change level 3 (###) to level 2 (##):

    sgit -e 's/^### \(Alternate code\)/## \1/g' '*README.md'

which is the same as:

    sgit -e 's/^### Alternate code/## Alternate code/g' '*README.md'

This is per discussion in GitHub.

1998/dlowe/README.md

@@ -27,7 +27,7 @@ make all
 
 Why is there different output?
 
-### Alternate code:
+## Alternate code:
 
 NOTE: The original entry was just a text based pootifier.  To build
 that version try:

1998/schweikh1/README.md

@@ -28,7 +28,7 @@ how to use it.
 NOTE: a limitation with the entry was that it required `gcc` but this limitation
 has been removed to make it more portable, requiring only `cc`.
 
-### Alternate code:
+## Alternate code:
 
 As noted above this entry will not work as it stands for macOS and there are
 some important notes as well as a description of how the fixed version works