Add compat to stdlibs in Project.toml (#285)

We need the <0.0.1 for compatibility with versions of Julia that do not allow upgradable stdlibs.

Project.toml

@@ -13,15 +13,18 @@ SparseArrays = "2f01184e-e22b-5df5-ae63-d93ebab69eaf"
 
 [compat]
 MathOptInterface = "1.20"
+Pkg = "<0.0.1, ^1.6"
 Requires = "1"
 SCS_GPU_jll = "=3.2.3"
 SCS_MKL_jll = "=3.2.2, =3.2.3"
 SCS_jll = "=3.2.1, =3.2.3"
+SparseArrays = "<0.0.1, ^1.6"
+Test = "<0.0.1, ^1.6"
 julia = "1.6"
 
 [extras]
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
 
 [targets]
-test = ["Test", "Pkg"]
+test = ["Pkg", "Test"]