Use a relative source path for DGP downgrade

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>

Author: ChrisRackauckas

test/DGP/Project.toml

@@ -12,7 +12,7 @@ Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [sources]
-SymbolicAnalysis = {path = "/home/crackauc/sandbox/tmp_20260715_055953_80193/audit/worktrees/symbolicanalysis-downgrade-current"}
+SymbolicAnalysis = {path = "../.."}
 
 [compat]
 LinearAlgebra = "1.10"