Match the vulkan config to the canonical exporter spec

The published config dropped int8's default flag and declared the encode
input as -1. The canonical schema marks one default per quant-group, and the
other whisper backends declare the encode length as its 480000 maximum.

vulkan/config.json

@@ -9,9 +9,9 @@
   "license": "apache-2.0",
   "variants": [
     {
-      "file": "whisper_tiny_vulkan_fp16.pte",
-      "precision": "fp16",
-      "quantized": false,
+      "file": "whisper_tiny_vulkan_int8.pte",
+      "precision": "int8",
+      "quantized": true,
       "default": true,
       "methods": {
         "decode": {
@@ -53,7 +53,7 @@
           "inputs": [
             {
               "shape": [
-                -1
+                480000
               ],
               "dtype": "float32"
             }
@@ -72,9 +72,10 @@
       }
     },
     {
-      "file": "whisper_tiny_vulkan_int8.pte",
-      "precision": "int8",
-      "quantized": true,
+      "file": "whisper_tiny_vulkan_fp16.pte",
+      "precision": "fp16",
+      "quantized": false,
+      "default": true,
       "methods": {
         "decode": {
           "inputs": [
@@ -115,7 +116,7 @@
           "inputs": [
             {
               "shape": [
-                -1
+                480000
               ],
               "dtype": "float32"
             }