Fix UnicodeEncodeError by using UTF-8 encoding for migration files (closes tortoise#2096) (tortoise#2097)

* Fix UnicodeDecodeError when loading migration files

* Fix UnicodeDecodeError when loading migration files

* style: fix ruff formatting

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Co-authored-by: 楚伟 <395150457@qq.com>

Author: chuwei-dev

tortoise/migrations/writer.py

@@ -263,7 +263,7 @@ def path(self) -> Path:
 
     def write(self) -> Path:
         path = self.path()
-        path.write_text(self.as_string(), encoding="ascii")
+        path.write_text(self.as_string(), encoding="utf-8")
         return path
 
     def as_string(self) -> str: