imbuf: Add regression test for PSD

Make use of recently added PSD test files to ensure loading works
correctly when we update our library dependencies.

Pull Request: https://projects.blender.org/blender/blender/pulls/123861

tests/python/bl_imbuf_load.py

@@ -156,6 +156,9 @@ class ImBufLoadTest(ImBufTest):
 
         self.check("*.webp")
 
+    def test_load_psd(self):
+        self.check("*.psd")
+
 
 class ImBufBrokenTest(AbstractImBufTest):
     @classmethod