Update mp4 rev (#7382)

### What

- Update `mp4` to latest `main`, fixing panic when loading files with
multiple tracks (audio and video)

### Checklist
* [x] I have read and agree to [Contributor
Guide](https://github.com/rerun-io/rerun/blob/main/CONTRIBUTING.md) and
the [Code of
Conduct](https://github.com/rerun-io/rerun/blob/main/CODE_OF_CONDUCT.md)
* [x] I've included a screenshot or gif (if applicable)
* [x] I have tested the web demo (if applicable):
* Using examples from latest `main` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7382?manifest_url=https://app.rerun.io/version/main/examples_manifest.json)
* Using full set of examples from `nightly` build:
[rerun.io/viewer](https://rerun.io/viewer/pr/7382?manifest_url=https://app.rerun.io/version/nightly/examples_manifest.json)
* [x] The PR title and labels are set such as to maximize their
usefulness for the next release's CHANGELOG
* [x] If applicable, add a new check to the [release
checklist](https://github.com/rerun-io/rerun/blob/main/tests/python/release_checklist)!
* [x] If have noted any breaking changes to the log API in
`CHANGELOG.md` and the migration guide

- [PR Build Summary](https://build.rerun.io/pr/7382)
- [Recent benchmark results](https://build.rerun.io/graphs/crates.html)
- [Wasm size tracking](https://build.rerun.io/graphs/sizes.html)

To run all checks from `main`, comment on the PR with `@rerun-bot
full-check`.

Cargo.lock

@@ -3464,7 +3464,7 @@ dependencies = [
 [[package]]
 name = "mp4"
 version = "0.14.0"
-source = "git+https://github.com/rerun-io/mp4?rev=523ebcc71032e7022335f61d7314b89f6068208a#523ebcc71032e7022335f61d7314b89f6068208a"
+source = "git+https://github.com/rerun-io/mp4?rev=ef529032547d7f97161e95c58bd76856cb116349#ef529032547d7f97161e95c58bd76856cb116349"
 dependencies = [
  "byteorder",
  "bytes",

Cargo.toml

@@ -537,8 +537,8 @@ egui_tiles = { git = "https://github.com/rerun-io/egui_tiles", rev = "b2f5e23252
 # egui_commonmark = { git = "https://github.com/rerun-io/egui_commonmark", rev = "63d5c8933445b9ea9088c4a50b71f4ede1f3c247" } # https://github.com/lampsitter/egui_commonmark/pull/51
 
 # commit on `rerun-io/mp4` `main` branch
-# https://github.com/rerun-io/mp4/commit/523ebcc71032e7022335f61d7314b89f6068208a
-mp4 = { git = "https://github.com/rerun-io/mp4", rev = "523ebcc71032e7022335f61d7314b89f6068208a" }
+# https://github.com/rerun-io/mp4/commit/ef529032547d7f97161e95c58bd76856cb116349
+mp4 = { git = "https://github.com/rerun-io/mp4", rev = "ef529032547d7f97161e95c58bd76856cb116349" }
 
 # commit on `rerun-io/re_arrow2` `main` branch
 # https://github.com/rerun-io/re_arrow2/commit/e4717d6debc6d4474ec10db8f629f823f57bad07