use max of 32 dataset processes if not explicit

[winglian]

should help with #2395 @NanoCode012

[NanoCode012]

The reason I mentioned 32 was because we had (in several places), a max of 64.

axolotl/src/axolotl/datasets.py

Line 49 in 4a73698

num_proc = min(64, self.process_count if self.process_count else os.cpu_count())

axolotl/src/axolotl/core/datasets/chat.py

Line 46 in 4a73698

num_proc = min(64, process_or_cpu_count)

We should probably consolidate this.