Remove preset_tests from docs

CONTRIBUTING_MODELS.md

@@ -35,7 +35,6 @@ Keep this checklist handy!
 ### Step 4: PR #3 - Add XX Presets
 
 - [ ] An `xx/xx_presets.py` file with links to weights uploaded to a personal GCP bucket/Google Drive \[[Example](https://github.com/keras-team/keras-nlp/blob/master/keras_nlp/models/distil_bert/distil_bert_presets.py)\].
-- [ ] An `xx/xx_presets_test.py` file with runnable tests for each preset \[[Example](https://github.com/keras-team/keras-nlp/blob/master/keras_nlp/models/distil_bert/distil_bert_presets_test.py)\].
 - [ ] A `tools/checkpoint_conversion/convert_xx_checkpoints.py` which is reusable script for converting checkpoints \[[Example](https://github.com/keras-team/keras-nlp/blob/master/tools/checkpoint_conversion/convert_distilbert_checkpoints.py)\].
 - [ ] A Colab notebook link in the PR description, showing an end-to-end task such as text classification, etc. The task model can be built using the backbone model, with the task head on top \[[Example](https://gist.github.com/mattdangerw/bf0ca07fb66b6738150c8b56ee5bab4e)\].