Remove NFT Gallery

[navi-arneja]

For resubmission of the macOS version for the app store we need the following to be updated for version 1.3.4:

• Disable NFT Gallery & remove it from the side navigation. This means the "NFT gallery is unavailable" modal no longer will show up

For the next version:

• In a separate PR, please include the following alert message banner that displays on wallet load. The user should be able to dismiss the alert for their current session.

Designs: https://www.figma.com/file/KyMmhh4XU31uzaPO1oTvwY/Tokens%2FNFTs%2FAlerts?node-id=1722%3A1609

FAQ link: https://cryptonomic.zendesk.com/hc/en-us/articles/5868256903053-The-NFT-gallery-and-dapp-interactions-are-unavailable-