Fix typo in README regarding pickle loading

Author: ae-foster

README.md

@@ -64,7 +64,7 @@ We recommend using distinct output directories for every training run.
 Regarding other optional arguments, run `python scripts/transferable.py -h` for more information.
 
 **Note**: Checkpoints are stored using `pickle`. This means that opening a checkpoint from an untrusted source is a major security risk. Only ever open checkpoint files from trusted sources. To prevent reading untrusted pickle files, checkpoint reading is disabled by default and can be
-re-enabled by settings the environment variable `ORBFORMER_PICKLE_LOADING=1`.
+re-enabled by setting the environment variable `ORBFORMER_PICKLE_LOADING=1`.
 
 ### Preparing new structure data for fine-tuning