Merge pull request #439 from SciML/compathelper/new_version/2021-08-31-00-48-03-962-02398127852

CompatHelper: bump compat for SymbolicUtils to 0.15 for package perturbation, (keep existing compat)

Author: ChrisRackauckas

tutorials/perturbation/Project.toml

@@ -11,5 +11,5 @@ DifferentialEquations = "6.17"
 ModelingToolkit = "5.17, 6"
 Plots = "1.16"
 SciMLTutorials = "0.9"
-SymbolicUtils = "0.11, 0.12, 0.13"
+SymbolicUtils = "0.11, 0.12, 0.13, 0.14, 0.15"
 Symbolics = "0.1, 1, 2, 3"