ci: add SciMLSensitivity/Core8 to downstream CI

Author: AayushSabharwal

.github/workflows/Downstream.yml

@@ -38,6 +38,7 @@ jobs:
           - {user: SciML, repo: MethodOfLines.jl, group: 2D_Diffusion}
           - {user: SciML, repo: MethodOfLines.jl, group: DAE}
           - {user: SciML, repo: ModelingToolkitNeuralNets.jl, group: All}
+          - {user: SciML, repo: SciMLSensitivity.jl, group: Core8}
 
           - {user: Neuroblox, repo: Neuroblox.jl, group: All}
     steps: