[Dependabot]: Update pyvhdlmodel requirement from ~=0.29.2 to ~=0.31.0

Updates the requirements on [pyvhdlmodel](https://GitHub.com/VHDL/pyVHDLModel) to permit the latest version.
- [Commits](https://GitHub.com/VHDL/pyVHDLModel/compare/v0.29.2...v0.31.0)

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

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

requirements.txt

@@ -1,3 +1,3 @@
 pyTooling ~= 8.2
-pyVHDLModel ~= 0.29.2
+pyVHDLModel ~= 0.31.0
 py-flags ~= 1.1