randomize seed phrase backup .txt file name

[dpazdan]

What problem are you trying to solve?
When someone clicks on:

Download this Secret Backup Phrase and keep it stored safely on an external encrypted hard drive or storage medium.

It will download a file that is named: MetaMask Secret Backup Phrase.txt. This can be used by anyone that knows this to search computers for the file that holds clear text seed phrases.

Describe the solution you'd like
For security purposes, we should randomize the name of the file. Or at a minimum we should state clearly in the instructions, that the user should rename the file.

Change to:
Download this Secret Backup Phrase

1. rename the file.
2. keep it stored safely on an external encrypted hard drive or storage medium.

reference: https://www.reddit.com/r/Metamask/comments/e90pae/key_file_download/