Update pyside2 requirement from >=5.15.0 to >=5.13.2

Updates the requirements on [pyside2](https://www.pyside.org) to permit the latest version.

---
updated-dependencies:
- dependency-name: pyside2
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <[email protected]>

requirements.txt

@@ -10,5 +10,5 @@ pynivision >= 2015.0.0
 # PyQt5 >= 5.12
 # PySide2 is LGPL-licensed
 # If PyQtGraph cannot find PySide2, please recreate the virtualenv.
-pyside2 >= 5.15.0
+pyside2 >= 5.13.2
 pyqtgraph >= 0.11.0