build: bump SymbolicUtils compat

Author: AayushSabharwal

lib/ModelingToolkitBase/Project.toml

@@ -158,7 +158,7 @@ StaticArrays = "1.9.14"
 StochasticDelayDiffEq = "1.11"
 StochasticDiffEq = "6.82.0"
 SymbolicIndexingInterface = "0.3.39"
-SymbolicUtils = "4.12"
+SymbolicUtils = "4.15.1"
 Symbolics = "7.8"
 UnPack = "0.1, 1.0"
 julia = "1.9"