Remove Julia v1.9 version checks from test suite

Since Julia v1.10 is now the LTS version, version checks for Julia v1.9
are no longer needed. This commit removes the conditional execution of
AD tests based on Julia version while keeping the tests themselves.

The VERSION >= v"1.9" conditions are now always true, so they have been removed.

🤖 Generated with [Claude Code](https://claude.ai/code)

Co-Authored-By: Claude <[email protected]>

Author: claude

test/runtests.jl

@@ -32,10 +32,10 @@ end
         @safetestset "Utils Tests" begin
             include("utils.jl")
         end
-        VERSION >= v"1.9" && @safetestset "AD Tests" begin
+        @safetestset "AD Tests" begin
             include("ADtests.jl")
         end
-        VERSION >= v"1.9" && @safetestset "AD Performance Regression Tests" begin
+        @safetestset "AD Performance Regression Tests" begin
             include("AD_performance_regression.jl")
         end
         @safetestset "Optimization" begin