[empath-split] End module names with : in manfests

This makes better distinction of module names and function lists.
Suggested by by @sbc100
(emscripten-core#25577 (comment)).

This has to land after
WebAssembly/binaryen#8003.

Author: aheejin

tools/empath-split.py

@@ -337,7 +337,7 @@ def main():
             print('    ' + func)
         print()
 
-      f.write(f'{module}\n')
+      f.write(f'{module}:\n')
       for func in funcs:
         f.write(func + '\n')
     f.close()