Show warning when ids are dropped because under threshold

[mmc46]

Currently ids are dropped without warning if it has no partners with connectivity above threshold (default is threshold = 5).
It would be useful to show a warning.

In the example below, the id 720575940622805700 is dropped.

cf_cosine_plot(cf_ids(malecns = "/type:DNge15(4|6)"
,
                      flywire = c("720575940622805700", "720575940636671886")),
               labRow = "{type}_{coconatfly::abbreviate_datasets(dataset)}_{group}_{side}",
               interactive = FALSE
, margins = c(15,10)
)