refactor(ast): update get_scopes method signature's typing to include None

Author: gnikit

fortls/parsers/internal/ast.py

@@ -168,11 +168,11 @@ def add_error(self, msg: str, sev: int, ln: int, sch: int, ech: int = None):
     def start_ppif(self, line_number: int):
         self.pp_if.append([line_number - 1, -1])
 
-    def end_ppif(self, line_number):
+    def end_ppif(self, line_number: int):
         if len(self.pp_if) > 0:
             self.pp_if[-1][1] = line_number - 1
 
-    def get_scopes(self, line_number: int = None):
+    def get_scopes(self, line_number: int | None = None):
         """Get a list of all the scopes present in the line number provided.
 
         Parameters