FCP on tracking issues is confusing

[remram44]

When proposing to enter FCP, rfcbot announces that it will "merge" the tracking issue. This makes no sense and it is pretty confusing for newcomers what this means, even if they are familiar with GitHub.

In practice, the bot doesn't appear to do anything to the issue when FCP is over, apart from announcing "The final comment period is now complete" in a comment. Someone then has to make a new PR to stabilize the feature and merge it.

Example: rust-lang/rust#44705 (and other tracking issues).