more fixes 20240228 (#1342) [skip ci]

* add missing evals_per_epoch setting

* more pydantic fixes

* more fixes

* move test from normalization to validation

* increase eval size for sample packing tests

src/axolotl/utils/config/__init__.py

@@ -164,9 +164,6 @@ def normalize_config(cfg):
         ]
     ) or cfg.is_qwen_derived_model
 
-    if isinstance(cfg.learning_rate, str):
-        cfg.learning_rate = float(cfg.learning_rate)
-
     if isinstance(cfg.pretraining_dataset, dict):
         cfg.pretraining_dataset = [cfg.pretraining_dataset]