Update SKP version

infra/bots/tasks.json

 {
   "jobs": {
     "Build-Ubuntu-GCC-x86_64-Release-GN": {
       "priority": 0.8,
       "tasks": [
         "Build-Ubuntu-GCC-x86_64-Release-GN"
       ]
     },
     "Build-Win-Clang-arm64-Release-GN_Android": {
       "priority": 0.8,
@@ skipping 155 matching lines @@
     "Perf-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-GN": {
       "cipd_packages": [
         {
           "name": "skia/bots/skimage",
           "path": "skimage",
           "version": "version:11"
         },
         {
           "name": "skia/bots/skp",
           "path": "skp",
-          "version": "version:14"
+          "version": "version:15"
         },
         {
           "name": "skia/bots/svg",
           "path": "svg",
           "version": "version:3"
         }
       ],
       "dependencies": [
         "Build-Ubuntu-GCC-x86_64-Release-GN"
       ],
@@ skipping 25 matching lines @@
     "Test-Android-Clang-AndroidOne-GPU-Mali400MP2-arm-Release-GN_Android": {
       "cipd_packages": [
         {
           "name": "skia/bots/skimage",
           "path": "skimage",
           "version": "version:11"
         },
         {
           "name": "skia/bots/skp",
           "path": "skp",
-          "version": "version:14"
+          "version": "version:15"
         },
         {
           "name": "skia/bots/svg",
           "path": "svg",
           "version": "version:3"
         }
       ],
       "dependencies": [
         "Build-Ubuntu-Clang-arm-Release-GN_Android"
       ],
@@ skipping 24 matching lines @@
     "Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-GN": {
       "cipd_packages": [
         {
           "name": "skia/bots/skimage",
           "path": "skimage",
           "version": "version:11"
         },
         {
           "name": "skia/bots/skp",
           "path": "skp",
-          "version": "version:14"
+          "version": "version:15"
         },
         {
           "name": "skia/bots/svg",
           "path": "svg",
           "version": "version:3"
         }
       ],
       "dependencies": [
         "Build-Ubuntu-GCC-x86_64-Release-GN"
       ],
@@ skipping 104 matching lines @@
         "revision=<(REVISION)",
         "patch_storage=<(PATCH_STORAGE)",
         "patch_issue=<(ISSUE)",
         "patch_set=<(PATCHSET)"
       ],
       "isolate": "upload_dm_results.isolate",
       "priority": 0.8
     }
   }
 }