Update vpu.json (#14612)

Update POT tool configs to use unified scales for concat by default.

Co-authored-by: Alexander Kozlov <alexander.kozlov@intel.com>
Co-authored-by: Liubov Talamanova <liubov.talamanova@intel.com>

tools/pot/openvino/tools/pot/configs/hardware/vpu.json

@@ -273,6 +273,15 @@
                 "activations": "q8_tn"
             }
         },
+        {
+            "type": "Concat",
+            "attributes": {
+                "unified_scales": "all"
+            },
+            "quantization": {
+                "activations": "q8_tn"
+            }
+        },
         {
             "type": "MVN",
             "quantization": {
@@ -280,7 +289,6 @@
             }
         },
         {"type": "Reshape"},
-        {"type": "Concat"},
         {"type": "Flatten"},
         {"type": "Squeeze"},
         {"type": "Unsqueeze"},