Restrict PythonCall to versions <0.9.29

See ReactionMechanismGenerator/RMG-Py#2861
In version 0.9.29 of PythonCall they dropped
support for verion 2.9 of Python,
which we currently need for_rmg.

Author: rwest

Project.toml

@@ -58,7 +58,7 @@ ModelingToolkit = "8"
 OrdinaryDiffEq = "^6"
 Parameters = "0.12"
 PreallocationTools = "0.4"
-PythonCall = "0.9"
+PythonCall = "0.9 - 0.9.28"
 PythonPlot = "1"
 QuartzImageIO = "0.7"
 RecursiveArrayTools = "2.17"