Changed YT label from "last updated" to "last checked"
Changed YT label from "last updated" to "last checked"

"updated" can be confusing if there is no new content.

PR 4523

lbryio/lbry-electron,lbryio/lbry-app,lbryio/lbry-electron,lbryio/lbry-app,lbryio/lbry-electron