Fix: API doc generation for bmesh opdefines

A continuation of the previous change. It was not enough to
simply point the script to the new file, the actual parsing
needed to be updated as well.

This is a minimalistic change which converts the file to the
old C-style format, just to restore the working state of the
CI/CD.

It is a bit fragile, and surely a more future-proof solution
is possible to work on.

Pull Request: https://projects.blender.org/blender/blender/pulls/110536

doc/python_api/rst_from_bmesh_opdefines.py

@@ -157,6 +157,8 @@ def main():
             l = l.strip()
             # casts
             l = l.replace("(int)", "")
+            l = re.sub(r'to_subtype_union\((.*?)\)', '{\\1}', l)
+            l = re.sub(r'eBMOpSlotSubType_Elem\((.*?)\)', '\\1', l)
 
             l = l.replace("{", "(")
             l = l.replace("}", ")")