Update NEX icon

[Olek97]

PLEASE READ AND DELETE THE CAPITALIZED TEXT, THE TITLE SECTION AND THE SECTION THAT DOESN'T APPLY BEFORE SUBMITTING.

DO NOT CLOSE AND REOPEN NEW PRS, UPDATE THE FIRST ONE YOU MADE.

READ CAREFULLY ALL THE FOLLOWING POINTS TO MAKE SURE YOUR PR ADHERES TO THE STANDARD TO AVOID UNNECESSARY BACK AND FORTH.

FAILURE TO READ BASIC INSTRUCTIONS WILL EVENTUALLY GET YOU BLOCKED FROM THE REPO.

Title

The title of your PR should be [CHAIN] Add NAME (SYMBOL) or Update NAME (SYMBOL). For example: [zilliqa] Add Zilstream (STREAM).

Icons requirements:

• Icons must be of type SVG or PNG.
• Max file size is 100KB.
• Icon must be a square, i.e, width and height of icon must be the same.
• Minimum length of icon must be 100px and maximum length of icon must be 500px.

Updating a token

• Make sure to rebase or clean your history
• PR doesn't have any merge conflict
• In case you are migrating a token, delete the old folder in the same PR