switch swift-tokenizers to main, remove some workarounds (#26)

* switch swift-tokenizers to main, remove some workarounds

- swift-tokenizers is getting a lot of updates and fixes, let's track main for now
- remove some workarounds that are no longer needed

- https://github.com/huggingface/swift-transformers/issues/63

mlx-swift-examples.xcodeproj/project.xcworkspace/xcshareddata/swiftpm/Package.resolved

@@ -59,8 +59,8 @@
       "kind" : "remoteSourceControl",
       "location" : "https://github.com/huggingface/swift-transformers",
       "state" : {
-        "revision" : "564442fba36b0b694d730a62d0593e5f54043b55",
-        "version" : "0.1.2"
+        "branch" : "main",
+        "revision" : "24605a8c0cc974bec5b94a6752eb687bae77db31"
       }
     }
   ],