avoid mutating original filesystem config when registering fsspec filesystems

Author: mrjsj

sqlmesh/core/config/connection.py

@@ -378,7 +378,7 @@ def init(cursor: duckdb.DuckDBPyConnection) -> None:
 
                 for file_system in self.filesystems:
                     options = file_system.copy()
-                    fs = file_system.pop("fs")
+                    fs = options.pop("fs")
                     fs = filesystem(fs, **options)
                     cursor.register_filesystem(fs)