tests: turn JuliaFormatter check to warn

Author: alyst

test/runtests.jl

@@ -1,7 +1,9 @@
 using Test, SafeTestsets, JuliaFormatter, StructuralEquationModels
 
 @testset "JuliaFormatter.jl" begin
-    @test format(StructuralEquationModels; verbose = false, overwrite = false)
+    if !format(StructuralEquationModels; verbose = false, overwrite = false)
+        @warn "Julia code formatting style inconsistencies detected."
+    end
 end
 @time @safetestset "Unit Tests" begin
     include("unit_tests/unit_tests.jl")