App: set high version in local dev to large number to avoid update prompt (#52385)

Set's a large version number when running `sg start app` so no updates
are found.

At first I disabled the updater in the dev conf, but doing that removes the
package and changes the rust lock file, this way we keep consistent
builds at the expense of a updater check at app launch.

src-tauri/tauri.dev.conf.json

@@ -1,5 +1,9 @@
 {
   "$schema": "../node_modules/@tauri-apps/cli/schema.json",
+  "package": {
+    "productName": "Sourcegraph",
+    "version": "9999.0.0"
+  },
   "tauri": {
     "bundle": {
       "externalBin": []