soften wording (recommended, not mandatory)

README.md

@@ -124,7 +124,7 @@ your training config (e.g. `models/heart_4x_pretrain.safetensors` for a 4x run).
   visible bright band + tile grid, worse with GAN loss.
 - Mild noise: `noise_range: [1,15]`, `noise_range2: [1,10]`.
 - Batch 2 is fine on a 12 GB card at lq96.
-- `--auto_resume` is **mandatory** when running train.py.
+- `--auto_resume` is recommended when running `train.py`.
 
 ### As a user (want to upscale images)