update to the newer version of `tokenizers`

tokenizer.json

@@ -991,7 +991,7 @@
       {
         "type": "Metaspace",
         "replacement": "▁",
-        "add_prefix_space": true
+        "prepend_scheme": "always"
       },
       {
         "type": "Split",
@@ -1104,7 +1104,7 @@
       {
         "type": "Metaspace",
         "replacement": "▁",
-        "add_prefix_space": false
+        "prepend_scheme": "always"
       },
       {
         "type": "Strip",