Fix: delete threshold for weight of bands

[dyzheng]

Reminder

• Have you linked an issue with this pull request?
• Have you noticed possible changes of behavior below or in the linked issue?
• Have you explained the changes of codes in core modules of ESolver, HSolver, ElecState, Hamilt, Operator or Psi? (ignore if not applicable)

Linked Issue

Fix #3251 .

What's changed?

• stress and force is sensitive with tiny weight bands, change threshold from 1e-10*weight_k to zero.

Any changes of core modules? (ignore if not applicable)

• Example: I have added a new virtual function in the esolver base class in order to ...