…runs" (#3850)

This reverts commit 12f6234.

The changes in [1] allowed TensorBoard to use the root directory's
projector config and apply it to each subdirectory.

If the root dir's config specifies a "sprite" that does not exist in every
subdirectory, it causes the Projector frontend to hang when loading a run.
See #3840 for details on
the issue.

Confirmed that this fixes the issue by running TB on a directory with:

- ./projector_config.pbtxt
```
embeddings {
  tensor_name: "EMNIST_Letters:0"
  metadata_path: "metadata.tsv"
  sprite {
    image_path: "sprite.png"
    single_image_dim: 28
    single_image_dim: 28
  }
}
```
- alongside a subdirectory `profile_demo_new` that contains a `.profile-empty` event file but no `sprite.png` file

[1] #3653