Numpy 1.25.0 will no longer support comparison to string

[CalCraven]

Coming up on unintended behavior when we try to compare attributes of a parametric potential to a null string with determining what to write for XML handling.

The line in question only works for numpy<=1.24.3. Probably can fix this single line so unyt arrays are not compared to this null string, and we can avoid that becoming an issue.

gmso/gmso/core/parametric_potential.py

Line 220 in e488a03

if value != ""

[CalCraven]

Issue is being discussed in unyt via:
yt-project/unyt#431

[CalCraven]

This is currently handled in GMSO by pinning to numpy<=1.24.3. I'm going to leave this issue open though, as a reminder that in the near future, we either need to get a fix on the unyt side, or fix our logic.

[daico007]

Resolved after #764