make test_activations less sensitive to random seed values

[jmitrevs]

Description

This rounds the inputs in test_activations in test_pytorch_api.py so that the input values are the same for both the pytorch and hls4ml models. This should decrease the sensitivity to random numbers, which caused for example, the test failure in #1200.

Type of change

• Other (Specify) - pytest robustness

Tests

Hopefully the pytest will no longer fail apparently randomly.

Checklist

• I have read the guidelines for contributing.
• I have commented my code, particularly in hard-to-understand areas.
• I have made corresponding changes to the documentation.
• My changes generate no new warnings.
• I have installed and run pre-commit on the files I edited or added.
• I have added tests that prove my fix is effective or that my feature works.