Able to add same/duplicate media to the playlist

[MadhaviSeelam]

Description

Description
Found while testing #32585. After adding a YT video to the playlist, click playlist icon again, clicked more media on this page same video information is shown

Steps to reproduce

1. Install 1.70.41
2. launched Brave
3. open a YT media (eg. https://www.youtube.com/watch?v=aVevvvvNYhM)
4. press playlist icon in URL bar
5. press Add Selected in the Add to Playlist dialog
6. select More media on this page from the menu

Actual result

Same video information is shown. Pressed Add selected, video was added to Playlist panel

2024-08-01_13h55_45.mp4

Expected result

User should not be able to same video again?

Reproduces how often

Easily reproduced

Brave version (brave://version info)

Brave	1.70.41 Chromium: 127.0.6533.88 (Official Build) nightly (64-bit)
Revision	9303bae9fe07bc2ec7c0cdef139e87304b2d6c96

Channel information

• release (stable)
• beta
• nightly

Reproducibility

• with Brave Shields disabled
• with Brave Rewards disabled
• in the latest version of Chrome

Miscellaneous information

@rebron @bsclifton
cc: @qa