Revert "syntax: Remove empty rules in regions"

This reverts commit a9b513a28a.

runtime/syntax/smalltalk.yaml

@@ -18,6 +18,7 @@ rules:
         start: "'"
         end: "'"
         skip: "\\\\."
+        rules: []
 
     - constant.string:
         start: "\""
@@ -49,5 +50,6 @@ rules:
     - constant.macro:
         start: "<<-?'?EOT'?"
         end: "^EOT"
+        rules: []
 
     - preproc.shebang: "^#!.+?( |$)"