train: escape the literal percent signs in two --help strings (argparse interpolates help text, so '+52 %' crashed --help with 'must be real number, not dict' -- caught by the CPU rehearsal's stage 3)

kernels/phase4_session.py

@@ -184,7 +184,7 @@ def main():
         "hubckpt.py": ("train/hubckpt.py",
                        "568c31b300906cb8d78a59ef890baa9731b18e064e3d69b0eaea4b45c546f23e"),
         "train_ounce100m.py": ("train/train_ounce100m.py",
-                               "60725990f1dc71160830ee03ec371cbcee8f70d7b13bf9a1b312188a0387b802"),
+                               "280f7ddc4632de30565426f1417f59c528a9ac0a59cfcfe18bc209216ede7c5e"),
     })
 
     import ounce100m_credentials