Language servers can take some time to respond to the
`textDocument/hover` and `textDocument/signatureHelp` messages. During
that time, the user could have already moved to another buffer. The
popup was always shown in the current buffer, which could be a different
one than the buffer for which the request was sent.
This was particularly annoying when moving to a buffer with a `BufLeave`
autocmd, as that autocmd was triggered when the hover popup was shown
for the original buffer.
Ignoring the response from these 2 messages if they are for a buffer
that is not the current one leads to less noise. The popup will only be
shown for the buffer for which it was requested.
A more robust solution could involve cancelling the hover/signatureHelp
request if the buffer changes so the language server can free its
resources. It could be implemented in the future.