Add v8.ignition_dispatches_table.json to .gitignore

R=rmcilroy@chromium.org
BUG=v8:4899
LOG=n

Review URL: https://codereview.chromium.org/1938673002 .

Cr-Commit-Position: refs/heads/master@{#35995}

.gitignore

@@ -90,3 +90,4 @@ gtags.files
 turbo*.cfg
 turbo*.dot
 turbo*.json
+v8.ignition_dispatches_table.json